Salt and photoresist composition containing the same

ABSTRACT

A salt represented by the formula (I):

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2017-194866 filed in JAPAN on Oct. 5, 2017,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention of the disclosure relates to a salt, and acid generatorcomprising the same, a photoresist composition and a method forproducing a photoresist pattern.

BACKGROUND OF THE INVENTION

US2006/194982A1 mentions the following salt and a photoresistcomposition comprising the same as an acid generator.

US2012/225385A1 mentions the following salt and a photoresistcomposition comprising the same as an acid generator.

SUMMARY OF THE INVENTION

The invention of the disclosure relates to the followings:

-   <1> A salt represented by the formula (I):

wherein Q¹ and Q² independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group,

-   R¹ and R² independently each represent a hydrogen atom, a fluorine    atom or a C1-C6 perfluoroalkyl group,-   z represents an integer of 0 to 6,-   L¹ represents a C1-C36 divalent hydrocarbon group which can have a    substituent and in which a methylene group can be replaced by —O—,    —S—, —CO— or —SO₂—,-   W¹ represents a C3-C18 cyclic hydrocarbon group which can have a    substituent and in which a methylene group can be replaced by —O—,    —S—, —CO— or —SO₂—,-   L² represents a single bond or a C1-C6 alkanediyl group which can    have a substituent and in which a methylene group can be replaced by    —O— or —CO—, and-   R³, R⁴ and R⁵ independently each represent a C1-C6 hydrocarbon group    in which a methylene group can be replaced by —O—, and-   Z⁺ represents an organic cation.-   <2> The salt according to <1>-   wherein L² represents a single bond or a C1-C6 alkanediyl group in    which a methylene group can be replaced by —O— or —CO—.-   <3> The salt according to <1> or <2>-   wherein L¹ represents a C1-C8 alkanediyl group in which a methylene    group can be replaced by —O— or —CO—, or a group composed of a C1-C4    alkanediyl group in which a methylene group can be replaced by —O—    or —CO— and a C3-C12 cyclic hydrocarbon group in which a methylene    group can be replaced by —O—, —S—, —CO— or —SO₂—.-   <4> The salt according to any one of <1> to <3>-   wherein W¹ represents an adamantane ring, a norbornane ring, a    norbornene ring, a cyclohexane ring or a norbornanelactone ring.-   <5> The salt according to any one of <1> to <4>-   wherein R⁵, R⁴ and R⁵ independently each represent a C1-C6 alkyl    group.-   <6> An acid generator comprising the salt according to any one of    <1> to <5>.-   <7> A photoresist composition comprising the acid generator    according to <6> and a resin which comprises a structural unit    having an acid-labile group.-   <8> The photoresist composition according to <7> which further    comprises a salt generating an acid weaker in acidity than an acid    generated from the acid generator.-   <9> A process for producing a photoresist pattern comprising the    following steps (1) to (5):

(1) a step of applying the photoresist composition according to <7> or<8> on a substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film thereby forming aphotoresist pattern.

DESCRIPTION OF EMBODIMENTS

The salt of the disclosure is represented by the formula (I):

wherein Q¹ and Q² independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group,

R¹ and R² independently each represent a hydrogen atom, a fluorine atomor a C1 -C6 perfluoroalkyl group,

z represents an integer of 0 to 6,

L¹ represents a C1-C36 divalent hydrocarbon group which can have asubstituent and in which a methylene group can be replaced by —O—, —S—,—CO— or —SO₂—,

W¹ represents a C3-C18 cyclic hydrocarbon group which can have asubstituent and in which a methylene group can be replaced by —O—, —S—,—CO— or —SO₂—,

L² represents a single bond or a C1-C6 alkanediyl group which can have asubstituent and in which a methylene group can be replaced by —O— or—CO—, and

R³, R⁴ and R⁵ independently each represent a C1-C6 hydrocarbon group inwhich a methylene group can be replaced by —O—, and

Z⁺ represents an organic cation.

Hereinafter, the salt will be simply referred to as “salt (I)”. In thesalt (I), a structure having a negative charge represents “anion (I)”,and a structure having a positive charge represents “cation (I)”.

For Q¹m Q², R¹ and R², examples of a perfluoroalkyl group include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a nonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group.

Q¹ and Q² each independently preferably represent a fluorine atom or atrifluoromethyl group, and Q¹ and Q² are more preferably fluorine atoms.

R¹ and R² each independently preferably represent a hydrogen atom or afluorine atom.

z preferably represent 0.

For L¹, examples of a C1-C36 divalent hydrocarbon group include analkanediyl group, a divalent monocyclic or polycyclic saturatedhydrocarbon group, a divalent aromatic hydrocarbon group and anycombination of these groups.

Examples of an alkanediyl group include a linear chain alkanediyl groupsuch as a methylene group, an ethylene group, a propane-1,3-diyl group,a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diylgroup, and dodecane-1,12-diyl group; and

a branched chain alkanediyl group such as ethane-1,1-diyl group,propane-1,1-diyl group, propane-1,2-diyl group, propane-2,2-diyl group,pentane-2,4-diyl group, 2-methylpropane-1,3-diyl group,2-methylpropane-1,2-diyl group, pentane-1,4-diyl group and2-methylbutane-1,4-diyl group.

Examples of a divalent monocyclic saturated hydrocarbon group include acycloalkanediyl group such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, acyclohexene-3,6-diyl group and a cyclooctane-1,5-diyl group.

Examples of a divalent polycyclic saturated hydrocarbon group include anorbornane-1,4-diyl group, a norbornane-2,5-diyl group, a5-norbornene-2,3-diyl group, an adamantane-1,5-diyl group, andadamantane-2,6-diyl group.

Examples of a divalent aromatic hydrocarbon group include a phenylenegroup, a naphthylene group, an anthrylene group, a biphenylene group anda phenanthrylene group.

Examples of any combination of the above-mentioned groups include anycombination of an alkanediyl group and a cyclic hydrocarbon group,specifically -cycloalkanediyl-alkanediyl-,-alkanediyl-cycloalkanediyl-alkanediyl-, and -alkanediyl-aromatichydrocarbon group-.

For L¹, examples of a substituent which a hydrocarbon group can haveinclude a hydroxyl group, a cyano group, a carboxyl group, a C1-C12alkoxy group, a C2-C13 acyl group, a C2-C13 acyloxy group and anycombination of them.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group and a hexyloxy group.

Examples of the acyl group include an acetyl group, a propionyl groupand butyryl group.

Examples of the acyloxy group include an acetyloxy group, a propionyloxygroup and a butyryloxy group.

The hydrocarbon group represented by L¹ can have a substituent.

A methylene group in the hydrocarbon group represented by L¹ can bereplaced by —O—, —S—, —CO— or —SO₂—.

When a methylene group in a hydrocarbon group represented by L¹ has beenreplaced by —O—, —S—, —CO— or —SO₂—, the number of the methylene groupis to be included in the number of the carbon atoms in the hydrocarbongroup.

A hydrocarbon group represented by L¹ is preferably a C1-C8,specifically C1-C6, alkanediyl group, a C3-C18 divalent alicyclichydrocarbon group, or a divalent hydrocarbon group composed of a C3-C18divalent alicyclic hydrocarbon group and a C1-C6 alkanediyl group [inthe divalent hydrocarbon group, a methylene group can be replaced by —O—or —CO—], and more preferably a C1-C6 alkanediyl group in which amethylene group can be replaced by —O— or —CO—, a group represented by*1-A¹¹-X^(1A)-A¹²- where X^(1A) represents a C3-C18 divalent alicyclichydrocarbon group, A¹¹ and A¹² each independently represent a C1-C6alkanediyl group in which a methylene group can be replaced by —O— or—CO—, and *1 is a binding site to —C (R¹) (R²)— or —C(Q²)(Q²) -, or*1-A_(1A)-A¹³- where X^(1A) and *1 as defined above and A¹³ represents aC1-C6 alkanediyl group in which a methylene group can be replaced by —O—or —CO—.

X^(1A) is preferably a C3-C18 divalent alicyclic hydrocarbon group, morepreferably a cyclohexanediyl group or an adamantanediyl group, stillmore preferably an adamantanediyl group.

A¹¹ preferably a methylene group. A¹² and A¹³ preferably eachindependently represent. *2-CO—O—CH₂— or *2-O—CO—O—CH₂— where *2 is abinding site to —X^(1A)—.

L¹ is preferably a C1-C8 alkanediyl group in which a methylene group canbe replaced by —O— or —CO—, or a group composed of a C1-C4 alkanediylgroup in which a methylene group can be replaced by —O— or —CO— and aC3-C12 cyclic hydrocarbon group in which a methylene group can bereplaced by —O—, —S—, —CO— or —SO₂—, more preferably a C1-C8 alkanediylgroup in which a methylene group can be replaced. by —O— or —CO—.

A cyclic hydrocarbon group represented by W¹ may be a non-aromatichydrocarbon ring or an aromatic hydrocarbon ring. The non-aromatichydrocarbon ring may be a monocyclic one, a polycyclic one, or a spirocycle, which may have an unsaturated bond.

Examples of the non-aromatic hydrocarbon ring include a monocyclicnon-aromatic hydrocarbon group such as a cyclopropane, a cyclobutane, acyclopentane, a cyclohexane, a cyclooctane, a cyclononane, a cyclodecaneand a cyclododecane; and a polycyclic non-aromatic hydrocarbon groupsuch as a norbornane, a norbornene, an adamantane and a condensed ringcomposed of a norbornane and a cyclopentane.

The non-aromatic hydrocarbon ring has preferably 5 to 18, morepreferably 6 to 12, carbon atoms.

Examples of the aromatic hydrocarbon ring include an aromatichydrocarbon group such as a benzene, a naphthalene, a biphenyl, aphenanthrene and a binaphthalene.

The aromatic hydrocarbon ring has preferably 6 to 14, more preferably 6to 10, carbon atoms.

When a methylene group in a cyclic hydrocarbon group represented by W¹has been replaced by —O—, —S—, —CO— or —SO₂—, the number of themethylene group is to be included in the number of the carbon atoms inthe hydrocarbon group.

-   The cyclic hydrocarbon group represented by W¹ can have a    substituent.-   For W¹, examples of a substituent which a hydrocarbon group can have    include a hydroxyl group, a halogen atom, a cyano group, a C1-C12    alkyl group, a C1-C12 alkoxy group, a C2-C13 alkoxycarbonyl group, a    C2-C13 alkylcarbonyl group, a C2-C13 alkylcarbonyloxy group, a    C3-C12 alicyclic hydrocarbon group and any combination of them.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, an undecyl groupand a dodecyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, an octyloxy group, a2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, an undecyloxygroup and a dodecyloxy group.

Examples of the alkoxycarbonyl group include a methoxycarbonyl group, anethoxycarbonyl group and a butoxycarbonyl group.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group and a butyryloxy group.

Examples of the C3-C12 alicyclic hydrocarbon group include the followingones:

in which ** is a binding site to a hydrocarbon group.

For a substituent on the cyclic hydrocarbon group represented by W¹,examples of the combinations of the above-mentioned groups include agroup composed of a hydroxy group and a C1-C12 alkyl group and a groupcomposed of a C1-C12 alkyl group and a C6-C10 aromatic hydrocarbongroup.

Examples of the group composed of a hydroxy group and a C1-C12 alkylgroup include a C1-C12 hydroxyalkyl group such as a hydroxymethyl groupand a hydroxyethyl group.

Examples of the group composed of a C1-C12 alkyl group and a C6-C10aromatic hydrocarbon group include a C7-C12 aralkyl group such as abenzyl group.

W¹ is preferably a polycyclic hydrocarbon group which can have asubstituent and in which a methylene group has been replaced by —O—,—S—, —CO— or —SO₂—, more preferably an adamantane, a norbornane, anorbornene, a cyclohexane or a norbornanelactone, and still morepreferably an adamantane or a norbornanelactone.

For L², examples of an alkanediyl group include a linear chainalkanediyl group such as a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group; and

a branched chain alkanediyl group such as ethane-1,1-diyl group,propane-1,1-diyl group, propane-1,2-diyl group, propane-2,2-diyl group,pentane-2,4-diyl group, 2-methylpropane-1,3-diyl group,2-methylpropane-1,2-diyl group, pentane-1,4-diyl group and2-methylbutane-1,4-diyl group.

L² is preferably a single bond or a C1-C6 alkanediyl group in which amethylene group can be replaced by —O— or —CO—, more preferably a singlebond, a methylene group or an ethylene group, still more preferably asingle bond or a methylene group, and further more preferably a singlebond.

Examples of the hydrocarbon group represented by R³, R⁴ or R⁵ include achain hydrocarbon group, an alicyclic hydrocarbon group and an aromatichydrocarbon group. In the hydrocarbon group, a methylene group can bereplaced by —O—.

Examples of the chain hydrocarbon group include an alkyl group, analkenyl group and an alkynyl group.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group and a hexyl group.

Examples of the alkenyl group include a vinyl group (ethenyl group), anallyl group (2-propenyl group), and an isopropenyl group(1-methylethenyl group).

Examples of the alkynyl group include an ethynyl group, a propynylgroup, and a butynyl group.

Examples of the alicyclic hydrocarbon group include a cyclopropyl group,a cyclobutyl group, a cyclopentyl group and a cyclohexyl group.

Examples of the aromatic hydrocarbon group include a phenyl group.

Examples of the hydrocarbon group in which a methylene group has beenreplaced by an oxygen atom include a methoxy group, an ethoxy group, amethoxymethyl group, an ethoxymethyl group, and a methoxymethoxy group.

R³, R⁴ and R⁵ are each independently preferably a C1-C6 alkyl group,more preferably a C1-C4 alkyl group, and still more preferably a methylgroup.

Specific examples of the anion (I) include the following ones. Amongthem, preferred are those represented by formulae (Ia-1) to (Ia-32),more preferred are those represented by formulae (Ia-1) to (Ia-6),(Ia-15) to (Ia-19) and (Ia-29) to (Ia-32), and still more preferred arethose represented by formulae (Ia-1) to (Ia-4), (Ia-15) to (Ia-19) and(Ia-29) to (Ia-32).

Examples of the organic cation represented by Z⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation.

Among them, an organic sulfonium cation and an organic iodonium cationare preferred, and an arylsulfonium cation is more preferred.

Preferred examples of the cation include those represented by theformulae (b2-1), (b2-2), (b2-3) and (b2-4):

In the formulae (b2-1) to (b2-4), R^(b4), R^(b5) and R^(b6)independently represent a C1-C30 aliphatic hydrocarbon group, a C3-C36alicyclic hydrocarbon group and a C6-C36 aromatic hydrocarbon group. Thealiphatic hydrocarbon group can have a substituent selected from thegroup consisting of a hydroxy group, a C1-C12 alkoxy group, aC3-C12alicyclic hydrocarbon group and a C6-C18aromatic hydrocarbongroup. The alicyclic hydrocarbon group can have a substituent selectedfrom the group consisting of a halogen atom, a C1-C18 aliphatichydrocarbon group, a C2-C4 acyl group and a glycidyloxy group. Thearomatic hydrocarbon group can have a substituent selected from thegroup consisting of a halogen atom, a hydroxy group, a C1-C18 aliphatichydrocarbon group and a C1-C12 alkoxy group.

R^(b4) and R^(b5) can be bonded to form a ring together with theadjacent S⁺, and a methylene group in the ring may be replaced by —CO—,—O— or —SO—.

R^(b7) and R^(b9) are independently in each occurrence a hydroxy group,a C1-C12 aliphatic hydrocarbon group or a C1-C12 alkoxy group, m2 and n2independently represents an integer of 0 to 5.

R^(b9) and R^(b10) independently represent a C1-C36 aliphatichydrocarbon group or a C3-C36 alicyclic hydrocarbon group.

R^(b9) and R^(b10) can be bonded to form a ring together with theadjacent S⁺, and a methylene group in the divalent alicyclic hydrocarbongroup may be replaced by —CO—, —O— or —SO—.

R^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 alicyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group.

R^(b12) represents a C1-C12 aliphatic hydrocarbon group in which ahydrogen atom can be replaced by a C6-C18 aromatic hydrocarbon group, aC3-C18 saturated cyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group in which a hydrogen atom can be replaced by a C1-C12alkoxy group or a (C1-C12 alkyl)carbonyloxy group.

R^(b11) and R^(b12) can be bonded each other to form a C1-C10 divalentalicyclic hydrocarbon group which forms a 2-oxocycloalkyl group togetherwith the adjacent —CHCO—, and a methylene group in the divalentalicyclic hydrocarbon group may be replaced by —CO—, —O— or —SO—.

R^(b13), R^(b14), R^(b16), R^(b17) and R^(b18) independently represent ahydroxy group, a C1-C12 aliphatic hydrocarbon group or a C1-C12 alkoxygroup.

L^(b31) represents —S— or —O— and o2, p2,s2 and t2each independentlyrepresents an integer of 0 to 5, q2 and r2 each independently representsan integer of 0 to 4, and u2 represents 0 or 1.

Preferred examples of the aliphatic hydrocarbon group represented byR^(b4) to R^(b12) include an alkyl group such as a methyl group, anethyl group, a n-propyl group, an isopropyl group, a n-butyl group,sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, anoctyl group and 2-ethylhexyl group. The aliphatic hydrocarbon grouprepresented by R^(b9), R^(b10), R^(b11), and R^(b12) has preferably 1 to12 carbon atoms.

The alicyclic hydrocarbon group may be monocyclic or polycyclic one.Preferred examples of the monocyclic hydrocarbon group include acycloalkyl group such as a cyclopentyl group, a cyclohexyl group, amethylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl groupand a cyclooctyl group. Preferred examples of the polycyclic hydrocarbongroup include an adamantyl group, a norbornyl group and adecahydronaphthyl group, and the following groups.

The alicyclic hydrocarbon group represented by R^(b9), R^(b10), R^(b11)and R^(b12) has preferably 3 to 18 carbon atoms, more preferably 4 to 12carbon atoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, and amethylnorbornyl group.

The alicyclic hydrocarbon group in which a hydrogen atom has beenreplaced by an aliphatic hydrocarbon group has preferably 20 or lesscarbon atoms in total.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, tolyl group, xylyl group, cumenyl group, mesityl group,p-ethylphenyl group, p-tent-butylphenyl group, p-adamantylphenyl group,a biphenylyl group, a naphthyl group, a phenanthryl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group.

When the aromatic hydrocarbon group has an alicyclic hydrocarbon groupor an aliphatic hydrocarbon group, it is preferred that the alicyclichydrocarbon group and the aliphatic hydrocarbon group have respectively1 to 18 carbon atoms and 3 to 18 carbon atoms.

Examples of the aromatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an alkoxy group include p-methoxyphenyl group.

Examples of the aliphatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aromatic hydrocarbon group include a benzyl group, aphenethyl group, a phenylpropyl group, trityl group, naphthylmethylgroup, and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the acyl group include an acetyl group, a propionyl groupand a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of alkylcarbonyloxy group include a methylcarbonyloxy group, anethylcarbonyloxy group, a n-propylcarbonyloxy group, anisopropylcarbonyloxy group, a n-butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethyl hexylcarbonyloxy group.

The ring group formed by bonding R^(b4) and R^(b5) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring is generally 3 to 12-memberedone, preferably 3 to 7-membered one. Examples of the ring include thefollowing ones.

The ring group formed by bonding R^(b9) and R^(b10) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include a thiolan-1-ium ring(tetrahydrothiophenium ring), a thian-1-ium ring and a1,4-oxathian-4-ium ring.

The ring group formed by bonding R^(b11) and R^(b12) together with—CH—CO— may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include an oxocycloheptanering, an oxocyclohexane ring, an oxonorbornane ring, and anoxoadamantane ring.

Preferred examples of the cation for the acid generator include anarylsulfonium cation, specifically cation of formula (b2-1) and morespecifically a phenylsulfonium cation.

Preferably, the cation of formula (b2-1) has one or three phenyl groups.When the cation of formula (b2-1) has one phenyl group, it has further athiolan-1-ium ring or a 1,4-oxathian-4-ium ring.

Examples of the cation represented by the formula (b2-1) include thefollowings.

Examples of the cation represented by the formula (b2-2) include thefollowings.

Examples of the cation represented by the formula (b2-3) include thefollowings.

Examples of the cation represented by the formula (b2-4) include thefollowings.

Specific examples of the salt (I) include those as listed in followingTables.

In those tables, every character in each column represents a sign whichrepresents one of the chemical formulae specifically illustrated above.For example, the salt (I-1) consists of the anion of formula (Ia-1) andthe cation of formula (b2-c-1) as shown below.

TABLE 1 Salt (I) anion (I) Cation (I) (I-1) (Ia-1) (b2-c-1) (I-2) (Ia-2)(b2-c-1) (I-3) (Ia-3) (b2-c-1) (I-4) (Ia-4) (b2-c-1) (I-5) (Ia-5)(b2-c-1) (I-6) (Ia-6) (b2-c-1) (I-7) (Ia-7) (b2-c-1) (I-8) (Ia-8)(b2-c-1) (I-9) (Ia-9) (b2-c-1) (I-10) (Ia-10) (b2-c-1) (I-11) (Ia-11)(b2-c-1) (I-12) (Ia-12) (b2-c-1) (I-13) (Ia-13) (b2-c-1) (I-14) (Ia-14)(b2-c-1) (I-15) (Ia-1) (b2-c-10) (I-16) (Ia-2) (b2-c-10) (I-17) (Ia-3)(b2-c-10) (I-18) (Ia-4) (b2-c-10) (I-19) (Ia-5) (b2-c-10) (I-20) (Ia-6)(b2-c-10) (I-21) (Ia-7) (b2-c-10) (I-22) (Ia-8) (b2-c-10) (I-23) (Ia-9)(b2-c-10) (I-24) (Ia-10) (b2-c-10) (I-25) (Ia-11) (b2-c-10) (I-26)(Ia-12) (b2-c-10)

TABLE 2 Salt (I) anion (I) Cation (I) (I-27) (Ia-13) (b2-c-10) (I-28)(Ia-14) (b2-c-10) (I-29) (Ia-1) (b2-c-12) (I-30) (Ia-2) (b2-c-12) (I-31)(Ia-3) (b2-c-12) (I-32) (Ia-4) (b2-c-12) (I-33) (Ia-5) (b2-c-12) (I-34)(Ia-6) (b2-c-12) (I-35) (Ia-7) (b2-c-12) (I-36) (Ia-8) (b2-c-12) (I-37)(Ia-9) (b2-c-12) (I-38) (Ia-10) (b2-c-12) (I-39) (Ia-11) (b2-c-12)(I-40) (Ia-12) (b2-c-12) (I-41) (Ia-13) (b2-c-12) (I-42) (Ia-14)(b2-c-12) (I-43) (Ia-1) (b2-c-14) (I-44) (Ia-2) (b2-c-14) (I-45) (Ia-3)(b2-c-14) (I-46) (Ia-4) (b2-c-14) (I-47) (Ia-5) (b2-c-14) (I-48) (Ia-6)(b2-c-14) (I-49) (Ia-7) (b2-c-14) (I-50) (Ia-8) (b2-c-14) (I-51) (Ia-9)(b2-c-14) (I-52) (Ia-10) (b2-c-14) (I-53) (Ia-11) (b2-c-14) (I-54)(Ia-12) (b2-c-14) (I-55) (Ia-13) (b2-c-14) (I-56) (Ia-14) (b2-c-14)(I-57) (Ia-1) (b2-c-27) (I-58) (Ia-2) (b2-c-27) (I-59) (Ia-3) (b2-c-27)(I-60) (Ia-4) (b2-c-27) (I-61) (Ia-5) (b2-c-27) (I-62) (Ia-6) (b2-c-27)(I-63) (Ia-7) (b2-c-27) (I-64) (Ia-8) (b2-c-27) (I-65) (Ia-9) (b2-c-27)(I-66) (Ia-10) (b2-c-27) (I-67) (Ia-11) (b2-c-27) (I-68) (Ia-12)(b2-c-27) (I-69) (Ia-13) (b2-c-27) (I-70) (Ia-14) (b2-c-27) (I-71)(Ia-1) (b2-c-30) (I-72) (Ia-2) (b2-c-30) (I-73) (Ia-3) (b2-c-30) (I-74)(Ia-4) (b2-c-30) (I-75) (Ia-5) (b2-c-30) (I-76) (Ia-6) (b2-c-30) (I-77)(Ia-7) (b2-c-30) (I-78) (Ia-8) (b2-c-30)

TABLE 3 Salt (I) anion (I) Cation (I) (I-79) (Ia-9) (b2-c-30) (I-80)(Ia-10) (b2-c-30) (I-81) (Ia-11) (b2-c-30) (I-82) (Ia-12) (b2-c-30)(I-83) (Ia-13) (b2-c-30) (I-84) (Ia-14) (b2-c-30) (I-85) (Ia-1)(b2-c-31) (I-86) (Ia-2) (b2-c-31) (I-87) (Ia-3) (b2-c-31) (I-88) (Ia-4)(b2-c-31) (I-89) (Ia-5) (b2-c-31) (I-90) (Ia-6) (b2-c-31) (I-91) (Ia-7)(b2-c-31) (I-92) (Ia-8) (b2-c-31) (I-93) (Ia-9) (b2-c-31) (I-94) (Ia-10)(b2-c-31) (I-95) (Ia-11) (b2-c-31) (I-96) (Ia-12) (b2-c-31) (I-97)(Ia-13) (b2-c-31) (I-98) (Ia-14) (b2-c-31) (I-99) (Ia-15) (b2-c-1)(I-100) (Ia-16) (b2-c-1) (I-101) (Ia-17) (b2-c-1) (I-102) (Ia-18)(b2-c-1) (I-103) (Ia-19) (b2-c-1) (I-104) (Ia-20) (b2-c-1) (I-105)(Ia-21) (b2-c-1) (I-106) (Ia-22) (b2-c-1) (I-107) (Ia-23) (b2-c-1)(I-108) (Ia-24) (b2-c-1) (I-109) (Ia-25) (b2-c-1) (I-110) (Ia-26)(b2-c-1) (I-111) (Ia-27) (b2-c-1) (I-112) (Ia-28) (b2-c-1) (I-113)(Ia-15) (b2-c-10) (I-114) (Ia-16) (b2-c-10) (I-115) (Ia-17) (b2-c-10)(I-116) (Ia-18) (b2-c-10) (I-117) (Ia-19) (b2-c-10) (I-118) (Ia-20)(b2-c-10) (I-119) (Ia-21) (b2-c-10) (I-120) (Ia-22) (b2-c-10)

TABLE 4 Salt (I) anion (I) Cation (I) (I-121) (Ia-23) (b2-c-10) (I-122)(Ia-24) (b2-c-10) (I-123) (Ia-25) (b2-c-10) (I-124) (Ia-26) (b2-c-10)(I-125) (Ia-27) (b2-c-10) (I-126) (Ia-28) (b2-c-10) (I-127) (Ia-15)(b2-c-12) (I-128) (Ia-16) (b2-c-12)

TABLE 5 Salt (I) anion (I) Cation (I) (I-129) (Ia-17) (b2-c-12) (I-130)(Ia-18) (b2-c-12) (I-131) (Ia-19) (b2-c-12) (I-132) (Ia-20) (b2-c-12)(I-133) (Ia-21) (b2-c-12) (I-134) (Ia-22) (b2-c-12) (I-135) (Ia-23)(b2-c-12) (I-136) (Ia-24) (b2-c-12) (I-137) (Ia-25) (b2-c-12) (I-138)(Ia-26) (b2-c-12) (I-139) (Ia-27) (b2-c-12) (I-140) (Ia-28) (b2-c-12)(I-141) (Ia-15) (b2-c-14) (I-142) (Ia-16) (b2-c-14) (I-143) (Ia-17)(b2-c-14) (I-144) (Ia-18) (b2-c-14) (I-145) (Ia-19) (b2-c-14) (I-146)(Ia-20) (b2-c-14) (I-147) (Ia-21) (b2-c-14) (I-148) (Ia-22) (b2-c-14)(I-149) (Ia-23) (b2-c-14) (I-150) (Ia-24) (b2-c-14) (I-151) (Ia-25)(b2-c-14) (I-152) (Ia-26) (b2-c-14) (I-153) (Ia-27) (b2-c-14) (I-154)(Ia-28) (b2-c-14)

TABLE 6 Salt (I) anion (I) Cation (I) (I-155) (Ia-15) (b2-c-27) (I-156)(Ia-16) (b2-c-27) (I-157) (Ia-17) (b2-c-27) (I-158) (Ia-18) (b2-c-27)(I-159) (Ia-19) (b2-c-27) (I-160) (Ia-20) (b2-c-27) (I-161) (Ia-21)(b2-c-27) (I-162) (Ia-22) (b2-c-27) (I-163) (Ia-23) (b2-c-27) (I-164)(Ia-24) (b2-c-27) (I-165) (Ia-25) (b2-c-27) (I-166) (Ia-26) (b2-c-27)(I-167) (Ia-27) (b2-c-27) (I-168) (Ia-28) (b2-c-27) (I-169) (Ia-15)(b2-c-30) (I-170) (Ia-16) (b2-c-30) (I-171) (Ia-17) (b2-c-30) (I-172)(Ia-18) (b2-c-30) (I-173) (Ia-19) (b2-c-30) (I-174) (Ia-20) (b2-c-30)(I-175) (Ia-21) (b2-c-30) (I-176) (Ia-22) (b2-c-30) (I-177) (Ia-23)(b2-c-30) (I-178) (Ia-24) (b2-c-30) (I-179) (Ia-25) (b2-c-30) (I-180)(Ia-26) (b2-c-30) (I-181) (Ia-27) (b2-c-30) (I-182) (Ia-28) (b2-c-30)(I-183) (Ia-15) (b2-c-31) (I-184) (Ia-16) (b2-c-31) (I-185) (Ia-17)(b2-c-31) (I-186) (Ia-18) (b2-c-31) (I-187) (Ia-19) (b2-c-31) (I-188)(Ia-20) (b2-c-31) (I-189) (Ia-21) (b2-c-31) (I-190) (Ia-22) (b2-c-31)

TABLE 7 Salt (I) anion (I) Cation (I) (I-191) (Ia-23) (b2-c-31) (I-192)(Ia-24) (b2-c-31) (I-193) (Ia-25) (b2-c-31) (I-194) (Ia-26) (b2-c-31)(I-195) (Ia-27) (b2-c-31) (I-196) (Ia-28) (b2-c-31) (I-191) (Ia-23)(b2-c-31) (I-192) (Ia-24) (b2-c-31) (I-193) (Ia-25) (b2-c-31) (I-194)(Ia-26) (b2-c-31) (I-195) (Ia-27) (b2-c-31) (I-196) (Ia-28) (b2-c-31)(I-197) (Ia-29) (b2-c-1) (I-198) (Ia-30) (b2-c-1) (I-199) (Ia-31)(b2-c-1) (I-200) (Ia-32) (b2-c-1) (I-201) (Ia-29) (b2-c-10) (I-202)(Ia-30) (b2-c-10) (I-203) (Ia-31) (b2-c-10) (I-204) (Ia-32) (b2-c-10)(I-205) (Ia-29) (b2-c-12) (I-206) (Ia-30) (b2-c-12) (I-207) (Ia-31)(b2-c-12) (I-208) (Ia-32) (b2-c-12) (I-209) (Ia-29) (b2-c-14) (I-210)(Ia-30) (b2-c-14) (I-211) (Ia-31) (b2-c-14) (I-212) (Ia-32) (b2-c-14)(I-213) (Ia-29) (b2-c-27) (I-214) (Ia-30) (b2-c-27) (I-215) (Ia-31)(b2-c-27) (I-216) (Ia-32) (b2-c-27) (I-217) (Ia-29) (b2-c-30) (I-218)(Ia-30) (b2-c-30) (I-219) (Ia-31) (b2-c-30) (I-220) (Ia-32) (b2-c-30)(I-221) (Ia-29) (b2-c-31) (I-222) (Ia-30) (b2-c-31) (I-223) (Ia-31)(b2-c-31) (I-224) (Ia-32) (b2-c-31)

Among these specific examples, preferred as the salt (I) are salt (I-1)to salt (I-4), salt (I-15) to salt (I-18), salt (I-29) to salt (I-32),salt (I-43) to salt (I-46), salt (I-57) to salt (I-60), salt (I-71) tosalt (I-74), salt (I-85) to salt (I-88), salt (I-99) to salt (I-103),salt (I-113) to salt (I-117), salt (I-127) to salt (I-131), salt (I-141)to salt (I-145), salt (I-155) to salt (I-159), salt (I-169) to salt(I-173), salt (I-183) to salt (I-187) and salt (I-197) to salt (I-224).

The process for producing the salt (I) will be illustrated.

The salt (I) can be produced by reacting a salt represented by theformula (I-a) with the compound represented by formula (I-b), in thepresence of a base such as triethylamine, pyridine, diethylaminopyridineand methylimidazole in a solvent such as dimethylformamide, chloroformor acetonitrile:

wherein Q¹, Q², L¹, L², W¹, R¹, R², R³, R⁴, R⁵, z and Z⁺ are the same asdefined above.

The above-mentioned reaction is usually conducted at about 5 to 80° C.typically for 0.5 to 24 hours.

Specific examples of the salt represented by the formula (I-a) includethe following ones. These salts can be prepared according to a method asrecited in JP2006-257078A1, JP2009-46479A1 or JP2012-193170A1.

Specific examples of the compound represented by the formula (I-b)include the following ones. The compound represented by the formula(I-b) is available on the market.

<Acid Generator>

The acid generator of the disclosure comprises the salt (I). The acidgenerator may contain two or more kinds of the salt (I). The acidgenerator may further contain one or more known acid generator inaddition to the salt (I).

In the photoresist composition, an acid generates from the acidgenerator by light for lithography. The acid catalytically acts againstan acid-labile group in the resin to cleave the acid-labile group.

The acid generator known in the art may be a nonionic acid generator oran ionic acid generator. Examples of the nonionic acid generator includean organo-halogen compound, a sulfonate compound such as a2-nitrobenzylsulfonate, an aromatic sulfonate, an oxime sulfonate, anN-sulfonyloxylmide, a sulfonyloxyketone and diazonaphthoquinone4-sulfonate, and a sulfone compound such as a disulfone, ketosulfone anda sulforiyldiazomethane. Examples of the ionic acid generator include anonium salt compound such as a diazonium salt, a phosphonium salt, asulfonium salt and an iodonium salt. Examples of the anion of the oniumsalt include a sulfonic acid anion, a sulfonylimide anion and asulfonylmethide anion.

Specific examples of the acid generator known in the art include acidgenerators described JP 63-26653 A, JP 55-164824 A, JP62-69263 A,JP63-146038A, JP63-163452A, JP62-153853A, JP63-146029A, U.S. Pat. Nos.3,779,778, 3,849,137, DE Patent No. 3914407 and EP Patent No. 126,712.Other examples of that include acid generators described inJP2013-68914A, JP2013-3155A and JP2013-11905A.

The acid generator known in the art is preferably a fluorine-containingacid generator, and more preferably a fluorine-containing organicsulfonate acid generator.

Preferable examples of the acid generator known in the art include asalt represented by the formula (B1):

wherein Q^(b1) and Q^(b2) each independently represent a fluorine atomor a C1-C6 perfluoroalkyl group,

L^(b1) represents a C1-C24 divalent saturated hydrocarbon group in whicha methylene group can be replaced by —O— or —CO— and in which a hydrogenatom can be replaced by a fluorine atom or a hydroxy group, and

Y represents a methyl group which can have a substituent or a C3-C18monovalent alicyclic hydrocarbon group which can have a substituent andin which a methylene group can be replaced by —O—, —CO— or —SO₂—, and

Z1⁺ represents an organic cation.

Hereinafter, the salt represented by the formula (B1) is sometimesreferred to as “Salt (B1)”.

For Q^(b1) and Q^(b2), examples of the perfluoroalkyl group includeexamples of those for Q¹ and Q², and a trifluoromethyl group ispreferred. Q^(b1) and Q^(b2) each independently preferably represent afluorine atom or a trifluoromethyl group, and Q^(b1) and Q^(b2) are morepreferably fluorine atoms.

For L^(b2), examples of the saturated hydrocarbon group in which amethylene group has been replaced by an oxygen atom or a carbonyl groupinclude those represented by formulae (b1-1), (b1-2) and (b1-3).

In formula (b1-1) L^(b2) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b2) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that total numberof the carbon atoms of L^(b2) and L^(b3) up to 22.

In formula (b1-2), L^(b4) represents a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, and L^(b5) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group, provided that the total carbon atomsof L^(b4) and L^(b5) is up to 22.

In formula (b1-3) L^(b6) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b7) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, with the proviso thattotal carbon number of L^(b6) and L^(b7) is up to 23 and with theproviso that formula (b1-3) excludes a group having a structurerepresented by -L^(b6)-O—CO—.

In these formulae, * represents a binding position to Y.

In formulae (b1-1), (b1-2) and (b1-3), the divalent saturatedhydrocarbon group includes linear chain alkanediyl groups, branchedchain alkanediyl groups, monocyclic or polycyclic divalent saturatedhydrocarbon groups, and a group combining two or more of theabove-mentioned groups.

L^(b2) is preferably a single bond.

L^(b3) is preferably a C1-C4 divalent saturated hydrocarbon group.

L^(b4) is preferably a C1-C8 divalent saturated hydrocarbon group wherea hydrogen atom may be replaced by a fluorine atom.

L^(b5) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b6) is preferably a single bond or a C1-C4 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom.

L^(b7) is preferably a single bond or a C1-C7 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group.

Among them, those of formulae (b1-1) and (b1-3) are preferred.

Examples of the group represented by formula (b1-1) include thoserepresented by formulae (b1-4), (b1-5), (b1-6), (b1-7) and (b1-8).

In formula (b1-4), L^(b8) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom or a hydroxyl group.

In formula (b1-5), L^(b9) represents a C1-C20 divalent saturatedhydrocarbon group, and L^(b10) represents a single bond or a C1-C19divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, provided that the totalcarbon atoms of L^(b10) and L^(b9)is up to 20.

In formula (b1-6), L^(b11) represents a C1-C21 divalent saturatedhydrocarbon group, and L^(b12) represents a single bond or a C1-C20divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b11) and L^(b12) is up to 21.

In formula (b1-7), L^(b13) represents a C1-C19 divalent saturatedhydrocarbon group, L^(b14) represents a single bond or a C1-C18 divalentsaturated hydrocarbon group, and L^(b13) represents a single bond or aC1-C18 divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b13), L^(b14) and L^(b15) is up to 19.

In formula (b1-8), L^(b16) represents a C1-C18 divalent saturatedhydrocarbon group, L^(b17) represents a C1-C18 divalent saturatedhydrocarbon group, and L^(b18) represents a single bond or a C1-C17divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b16), L^(b17) and L^(b18) is up to 19.

In these formulae, * represents a binding position, * represents abinding position to Y.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups.

Specific examples of the divalent saturated hydrocarbon group includethose as referred to for L^(b1).

L^(b8) is preferably a C1-C4 divalent saturated hydrocarbon group.

L^(b9) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b10) is preferably a single bond or a C1-C19 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b11) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b12) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b13) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b14) is preferably a single bond or a C1-C6 divalent saturatedhydrocarbon group.

L^(b15) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b16) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b17) is preferably a C1-C6 divalent saturated hydrocarbon group.

L^(b18) preferably a single bond or a C1-C17 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C4 divalentsaturated hydrocarbon group.

Examples of the group represented by formula (b1-3) include thoserepresented by formulae (b1-9) (b1-10) and (b1-11).

In formula (b1-9), L^(b19) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b20) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that the totalcarbon atoms of L^(b19) and L^(b20) is up to 23.

In formula (b1-10) L^(b21) represents a single bond or a C1-C21 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, L^(b22) represents a single bond or a C1-C21 divalentsaturated hydrocarbon group and represents a single bond or a C1-C21divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom and where a methylenegroup may be replaced by an oxygen atom or a carbonyl group, providedthat the total carbon atoms of L^(b21), L^(b22) and L^(b23)is up to 21.

In formula (b1-11), L^(b24) represents a C1-C21 divalent saturatedhydrocarbon group Where a hydrogen atom may be replaced by a fluorineatom, L^(b25) represents a C1-C21 divalent saturated hydrocarbon group,and L^(b26) represents a single bond or a C1-C20 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or a carbonyl group, provided that the total carbon atomsof L^(b24), L^(b25) and L^(b26) is up to 21.

In these formulae, * represents a binding position to Y.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups.

Specific examples of the divalent saturated hydrocarbon group includethose as referred to for L.

Examples of the divalent saturated hydrocarbon group where a methylenegroup has been replaced by an oxygen atom or a carbonyl group includewhat has an acyloxy group. In what has an acyloxy group, a hydrogen atommay be replaced by a hydroxyl group and a methylene group may bereplaced by an oxygen atom or a carbonyl group.

Examples of what has an acyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy groupand an adamantylcarbonyloxy group.

When a hydrogen atom has been replaced by a hydroxyl group or amethylene group has been replaced by an oxygen atom or a carbonyl groupin what has an acyloxy group, examples of such a group include anoxoadamantylcarbonyloxy group, a hydroxyadamantylcarbonyloxy group, anoxocyclohexylcarbonyloxy group, and a hydroxycyclohexylcarbonyloxygroup.

Examples of the group represented by formula (b1-4) include thefollowing ones.

Examples of the group represented by formula (b1-5) include thefollowing ones.

Examples of the group represented by formula (b1-6) include thefollowing ones.

Examples of the group represented by formula (b1-7) include thefollowing ones.

Examples of the group represented by formula (b1-8) include thefollowing ones.

Examples of the group represented by formula (b1-2) include thefollowing ones.

Examples of the group represented by formula (b1-9) include thefollowing ones.

Examples of the group represented by formula (b1-10) include thefollowing ones.

Examples of the group represented by formula (b1-11) include thefollowing ones.

The monovalent alicyclic hydrocarbon group for Y may be a monocyclic oneor polycyclic one such as a spiro ring.

Preferred examples of the al cyclic hydrocarbon group represented by Yinclude those represented by the formulae (Y1) to (Y11) and (Y36) to(Y38). Preferred examples of the alicyclic hydrocarbon group which isrepresented by Y and in which a methylene group has been replaced by—O—, —SO₂— or —CO— include those represented by the formulae (Y12) to(Y35) and (Y39) and (Y41).

Among the groups represented by the formulae, preferred are thoserepresented by formulae (Y1) to (Y20), (Y30), (Y31), (Y39) and (Y41);more preferred are those represented by the formulae (Y11), (Y15),(Y16), (Y20), (Y30), (Y31), (Y39) and (Y40); and still more preferredare those represented by the formulae (Y11), (Y15), (Y30), (Y39) and(Y40).

When Y has a spiro ring such as the groups represented by formulae (Y28)to (Y35), the spiro ring preferably has a fluorine atom on an alkanediylbetween two oxygen atoms. Furthermore, a methylene group attached to anoxygen atom in an alkanediyl group forming a ketal structure has notbeen replaced by a fluorine atom.

Substituents on the methyl group for Y include a halogen atom, ahydroxyl group, a C3-C16 alicyclic hydrocarbon group, a C6-C18 aromatichydrocarbon group, a glycidyloxy group, and —(CH₂)_(j2)—O—CO—R^(b1′)— inwhich R^(b1′) is a C1-C16 alkyl group and j2 is an integer of 0 to 4.

Substituents on the alicyclic hydrocarbon groups for Y include a halogenatom, a hydroxyl group, a C1-C12 alkyl group, a C1-C12hydroxy-containing alkyl group, a C1-C12 alkoxy group, a C3-C16alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon group, aC7-C21 aralkyl group, a C2-C4 acyl group, a glycidyloxy group, and—(CH₂)_(j2)—O—CO—R^(b1′)— in which R^(b1′) is a C1-C16 alkyl group andj2 is an integer of 0 to 4.

Substituents on the methyl group and the alicyclic hydrocarbon group forY does not have a silicon atom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a cycloheptyl group and a cyclooctyl group, anorbornyl group and an adamantyl group.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, a naphthyl group, an anthryl group, a p-methylphenylgroup, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolylgroup, a xylyl group, a cumyl group, a mesityl group, a biphenyl group,a phenanthryl group, a 2,6-diethylphenyl group and a2-methyl-6-ethylphenyl group.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group and a dodecyl group.

Examples of hydroxyl-containing alkyl group include a hydroxymethylgroup and a hydroxyethyl group.

Examples of the C1-C12 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxygroup, a heptyloxy group, an octyloxy group, a decyloxy group and adodecyloxy group.

Examples of the aralkyl group include a benzyl group, phenylpropylgroup, a phenethyl group, a naphthylmethyl group, or a naphthylethylgroup.

Examples of the acyl group include an acetyl group, a propionyl groupand a butyryl group.

Examples of Y include the groups as follow.

Y represents preferably a C3-C18 alicyclic hydrocarbon group which mayhave a substituent and in which a methylene group has been replaced by—O—, —SO₂— or —CO—, more preferably an adamantyl group which may have asubstituent and in which a methylene group has been replaced by —O—,—SO₂— or —CO— and stall more preferably an adamantyl group, ahydroxyadamantyl group, an oxoadamantyl group, or the following group.

where * represents a binding position.

Preferred examples of the sulfonic acid anion of the salt represented byformula (B1) include salts represented by the formulae (B1-A-1 ) to(B1-A-55), preferably the formulae (B1-A-1) to (B1-A-4), (B1-A-9),(B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40) and (B1-A-47)to (B1-A-55).

In these formulae, the symbols Q^(b1) and Q^(b2) are defined as above,R^(i2), R^(i3), R^(i4), R^(i5), R^(i6) and R^(i7) each independentlyrepresent a C1-C4 alkyl group, preferably a methyl group or a methylgroup, R^(i8) represents a C1-C12 aliphatic hydrocarbon group[preferably a C1-C4 alkyl group], a C5-C12monovalent alicyclichydrocarbon group, or a combined group of them, preferably a methylgroup, an ethyl group, a cyclohexyl group or an adamantyl group, andL^(A4) represents a single bond or a C1-C4 alkanediyl group.

Examples of the sulfonic acid anion of the salt represented by formula(B1) include those described in JP2010-2046465A1.

Specific examples of the sulfonic acid anion of the salt represented byformula (B1) include the following anions.

Among them, preferred are those represented by formulae (B1a-1) to(B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19) and (B1a-22) to(B1a-34).

Examples of the organic counter ion represented by Z1⁺ include an oniumcation such as a sulfonium cation, an iodonium cation, an ammoniumcation, a benzothiazolium cation and a phosphonium cation, specificallythe cations represented by formulae (b2-1) to (b2-4).

The salt represented by formula (B1) is preferably a salt which consistsof an anion represented by any one of formulae (B1a-1) to (B1a-3),(B1a-7) to (B1a-16), (B1a-18), (B1a-19) and (B1a-22) to (B1a-34) with acation represented by formula (b2-1) or (b2-3).

Specific examples of the salt represented by formula (B1) include thefollowing salts represented by formulae (B1-1) to (B1-48). Among them,those which comprise an arylsulfonium cation are preferred, the saltsrepresented by formulae (B1-1) to (B1-3), (B1-5) to (B1-7), (B1-11) to(B1-14), (B1-20) to (B1-26), (B1-29), (B1-31) to (B1-48) are morepreferred.

When the acid generator contains another salt than the salt (I), theweight ratio of salt (I) and the other salts is usually 1:99 to 99:1,preferably 2:98 to 98:2, more preferably 5:95 to 95:5, still morepreferably 10:90 to 90:10, and further more preferably 15:85 to 85:15.

The photoresist composition of the disclosure comprises the acidgenerator containing the salt (I) and a resin having an acid-labilegroup which resin is referred to as “Resin (A)”.

The photoresist composition may further contain another salt than thesalt (I) as an acid generator, a quencher, or solvent.

The content of the acid generator is preferably 1 to 40 parts by mass,more preferably 3 to 35 parts by mass, per 100 parts of Resin (A).

Resin (A) usually has a structural unit having an acid-labile group.Hereinafter, the structural unit is sometimes referred to as “structuralunit (a1)”.

Preferably Resin (A) further has another structural unit than thestructural unit (a1), i.e. a structural unit having no acid-labilegroup, which is sometimes referred to as “structural unit (s)”.

Herein, “an acid-labile group” means a group which has a hydrophilicgroup, such as a hydroxy group or a carboxy group, resulting fromremoving a leaving group therefrom by the action of an acid.

<Structural Unit (a1)>

The structural unit (a1) is derived from a compound having anacid-labile group which compound is sometimes referred to as “Monomer(a1)”.

For Resin (A), the acid-labile groups represented by formulae (1) and(2) are preferred.

In formula (1), R^(a1), R^(a2) and R^(a3) independently each represent aC1-C8 alkyl group, a C3-C20alicyclic hydrocarbon group or a groupconsisting of them, and R^(a1) and R^(a2) can be bonded each other toform a C3-C20 alicyclic hydrocarbon group together with the carbon atomto which R^(a1) and R^(a2) are bonded, “na” and “ma” each represent aninteger of 0 or 1 provided that at least one of them represents 1, andrepresents a binding position.

In formula (2), R^(a1′) and R^(a2′) independently each represent ahydrogen atom or a C1-C12 hydrocarbon group, and R^(a3′) represents aC1-C20 hydrocarbon group, and R^(a2′) and R^(3′) can be bonded eachother to form a C3-C20 heterocyclic group together with and the carbonatom to which R^(a2′) and R^(a3′) are bonded, and one or more in thehydrocarbon group and the heterocyclic group can be replaced by —O— or—S—, X represents an oxygen atom or a sulfur atom, “na′” represents aninteger of 0 or 1, and represents a binding position.

For R^(a1), R^(a2) and R^(a3), specific examples of the alkyl groupinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group andan octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group) and a polycyclic alicyclic hydrocarbon group such as adecahydronaphthyl group, an adamantyl group, a norbornyl group, and thefollowings:

in which * represents a binding position.

The alicyclic hydrocarbon group preferably has 3 to 16 carbon atoms.

Examples of the group consisting of alkyl and alicyclic hydrocarbongroup include a methylcyclohexyl group, a dimethylcyclohexyl group, amethylnorbornyl group, an adamantylmethyl group, and a norbornylethylgroup.

The “ma” is preferably 0. The “na” is preferably 1.

When the divalent hydrocarbon group is formed by bonding R^(a1) andR^(a2) each other, examples of the moiety —C(R^(a1))(R^(a2))(R^(a3))include the following groups and the divalent hydrocarbon grouppreferably has 3 to 12 carbon atoms.

wherein R^(a3) is the same as defined above and * represents a bindingposition.

For formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group anda group consisting of two or more of them.

Examples of the aliphatic hydrocarbon group and the alicyclichydrocarbon group include the same as described above. Examples of thearomatic hydrocarbon group include an aryl group such as a phenyl group,a naphthyl group, a p-methylphenyl group, a p-tert-butylphenyl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, amesityl group, a biphenyl group, an anthryl group, a phenanthryl group,a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the heterocyclic group formed by bonding R^(a2′) and R^(a3′)together with X and the carbon atom to which R^(a2′) and R^(a3′) arebonded include the following ones.

wherein * represents a binding position.

In formula (2), at least one of R^(a1′) and R^(a2′) is preferably ahydrogen atom. The “na′” is preferably 0.

Examples of the group represented by formula (1) include the followingones:

The group represented by formula (1) wherein R^(a1), R^(a2) and R^(a3)independently each represent a C1-C8 alkyl group, ma is 0, and na is 1,such as a terms-butyl group;

The group represented by formula (1) wherein R^(a1) and R^(a2) arebonded each other to form an adamantyl ring, R^(a3) is a C1-C8 alkylgroup, ma is 0, and na is 1, such as a 2-alkyl-2-adamantyl group;

The group represented by formula (1) wherein R^(a1) and R^(a2) are C1-C8alkyl groups, R^(a3) is an adamantyl group, ma is 0, and na is 1, suchas a 1-(1-adamantyl)-1-alkylalkoxycarbonyl group.

Specific examples of the group represented by formula (1) include thefollowings.

Specific examples of the group represented by formula (2) include thefollowings.

Monomer (al) is preferably a monomer having an acid-labile group in itsside chain and an ethylenic unsaturated group, more preferably a (meth)acrylate monomer having an acid-labile group in its side chain, andstill more preferably a (meth) acrylate monomer having the grouprepresented by formula (1) or (2).

The (meth)acrylate monomer having an acid-labile group in its side chainis preferably those which comprise a C5-C20 alicyclic hydrocarbon group.The resin which comprises a structural unit derived from such monomerscan provide improved resolution for a photoresist pattern to be preparedtherefrom.

The structural unit derived from a (meth) acrylate monomer having thegroup represented by formula (1) is preferably one of structural unitsrepresented by formulae (a1-0), (a1-1) and (a1-2).

In each formula, L^(a01), L^(a1) and L^(a2) each independently represent—O— or *—O—(CH₂)_(k1)—CO—O— in which k1 represents an integer of 1 to 7and * represents a binding position to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atomor a methyl group,

R^(a02), R^(a03), R^(a04), R^(a6) and R^(a7) each independentlyrepresent a C1-C8 alkyl group, a C3-C18 alicyclic hydrocarbon group, ora group formed by combining them,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

Hereinafter, the structural units represented by formulae (a1-0), (a1-1)and (a1-2) are referred to as “structural unit (a1-0)”, “structural unit(a1-1)” and “structural unit (a1-2)”, respectively.

Resin (A) may comprise two or more of such structural units.

L^(a01) is preferably *—O— or *—O—(CH₂)^(f1)—CO—O— in which * representsa binding position to —CO—, and f1 represents an integer of 1 to 4, andis more preferably *—O— or *—O—CH₂—CO—O—, and is especially preferably*—O—.

R^(a01) is preferably a methyl group.

For R^(a02), R^(a03) and R^(a04), examples of the alkyl group, thealicyclic hydrocarbon group and the group formed by combining theminclude the same as referred for R^(a1), R^(a2) and R^(a3).

The alkyl group preferably has 1 to 6 carbon atoms.

The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms andmore preferably 3 to 6 carbon atoms. The alicyclic hydrocarbon group ispreferably a saturated aliphatic cyclic hydrocarbon group. The groupformed by combining them preferably has 18 carbon atoms or less intotal, examples of which include a methylcyclonexyl group, adimethylcyclohexyl group, and a methylnorbornyl group.

Each of R^(a02) and R^(a03) is preferably a C1-C6 alkyl group, morepreferably a methyl group and an ethyl group.

R^(a04) is preferably a C1-C6 alkyl group and a C5-C12 alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group, and an adamantyl group.

Each of L^(a1) and L^(a2) Is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— inwhich * represents a binding position to —CO—, and f1 is the same asdefined above, and is more preferably *—O— or *—O—CH₂—CO—O—, and isespecially preferably *—O—.

Each of R^(a4) and R^(a5) is preferably a methyl group.

For R^(a6) and R^(a7), examples of the alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a tent-butyl group, a pentyl group, a heptyl group, a2-ethylheptyl group and an octyl group.

For R^(a6) and R^(a7), examples of the alicyclic hydrocarbon groupinclude a monocyclic alicyclic hydrocarbon group such as a cyclohexylgroup, a methylcyclohexyl group, a dimethylcyclohexyl group, acycloheptyl group and a methylcycloheptyl group, and a polycyclicalicyclic hydrocarbon group such as a decahydronaphthyl group, anadamantyl group, a norbornyl group, and a methylnorbornyl group.

For R^(a6) and R^(a7), examples of the group consisting of an alkylgroup and an alicyclic hydrocarbon group include an aralkyl group suchas a benzyl group, and a phenethyl group.

The alkyl group represented by R^(a6) and R^(a7) is preferably a C1-C6alkyl group, more preferably a methyl group, an ethyl group or anisopropyl group, and still more preferably an ethyl group, or anisopropyl group.

The alicyclic hydrocarbon group represented by R^(a6) and R^(a7) ispreferably a C3-C8 alicyclic hydrocarbon group, more preferably a C3-C6alicyclic hydrocarbon group.

The “m1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1′” is preferably 0 or 1.

Examples of the structural unit (a1-0) include those represented byformulae (a1-0-1) to (a1-0-12), preferably those represented by formulae(a1-0-1) to (a1-0-10).

Examples of the structural unit (a1-0) further include such groups thata methyl group corresponding to R^(a01) has been replaced by a hydrogenatom in any one of formulae (a1-0-1) to (a1-0-12).

Examples of the monomer from which the structural unit (a1-1) is derivedinclude the monomers described in JP2010-204646A1, and the followingmonomers represented by the formulae (a1-1-1) to (a1-1-4) and suchgroups that a methyl group has been replaced by a hydrogen atom in anyone of formulae (a1-1-1) to (a1-1-4), preferably the following monomersrepresented by the formulae (a1-1-1) to (a1-1-4).

Preferred examples of the structural unit (a1-2) include onesrepresented by formulae (a1-2-1) to (a1-2-6) and those represented bythe formulae in which a methyl group corresponding to R^(a5) has beenreplaced by a hydrogen atom, more preferably the monomers represented byformulae (a1-2-2), (a1-2-5) and (a1-2-6).

When the resin comprises one or more of the structural units representedby formulae (a1-0), (a1-1) and (a1-2), the total content of thestructural units is usually 10 to 95% by mole, preferably 15 to 90% bymole and more preferably 20 to 85% by mole, still more preferably 25 to70% by mole, and further more preferably 30 to 65% by mole, based on100% by mole of all the structural units of the resin.

Examples of the structural unit (a1) having the group represented byformula (2) include a structural unit represented by formula (a1-4). Thestructural unit is sometimes referred to as “structural unit (a1-4)”.

In the formula, R^(a32) represents a hydrogen atom, a halogen atom or aC1-C6 alkyl group that may have a halogen atom.

R^(a33) in each occurrence independently represent a halogen atom, ahydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acylgroup, a C2-C4 acyloxy group, an acryloyloxy group or methacryloyloxygroup, “1a” represents an integer 0 to 4,

R^(a34) and R^(a35) each independently represent a hydrogen atom or aC1-C12 hydrocarbon group; and

R^(a36) represents a C1-C20 hydrocarbon group, or R^(a35) and R^(a36)maybe bonded together with a C—O bonded thereto to form a divalentC3-C20 heterocyclic group, and a methylene group contained in thehydrocarbon group or the divalent heterocyclic group may be replaced byan oxygen atom or a sulfur atom.

Examples of the alkyl group of R^(a32) and R^(a32) include methyl,ethyl, propyl, isopropyl, butyl, pentyl and hexyl groups. The alkylgroup is preferably a C1-C4 alkyl group, and more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom of R^(a32) and R^(a23) include a fluorine,chlorine, bromine and iodine atoms.

Examples of the alkyl group that may have a halogen atom includetrifluoromethyl, difluoromethyl, methyl, perfluoroethyl,2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl,2,2,3,3,3-pentafluoropropyl, propyl, perfluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl,2,2,3,3,4,4,5,5,5-nonafluoropentyl, n-pentyl, n-hexyl andn-perfluorohexyl groups.

Examples of an alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy and hexyloxy groups. The alkoxy group is preferably a C1-C4alkoxy group, more preferably a methoxy group or an ethoxy group, andstill more preferably a methoxy group.

Examples of the acyl group include acetyl, propionyl and butyryl groups.Examples of the acyloxy group include acetyloxy, propionyloxy andbutyryloxy groups. Examples of the hydrocarbon group for R^(a34) andR^(a35) are the same examples as described in R^(a1′) to R^(a2′) in theformula (2).

Examples of hydrocarbon group for R^(a36) include a C1-C20 alkyl group,a C3-C18alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon groupor a group formed by combining thereof.

Examples of an alkyl group for R^(a36) include methyl, ethyl, propyl,isopropyl, butyl, pentyl, hexyl, octyl, decyl, and dodecyl groups.

Examples of an alicyclic hydrocarbon group for R^(a36) a C3-C18cycloalkyl groups such as a cyclopropyl group, a cyclohexyl group, and acyclooctyl group.

Examples of an aromatic hydrocarbon group for include phenyl group, anaphthyl group, an anthryl group, a biphenyl group, and a phenanthrylgroup.

Examples of a group formed by combining the above-mentioned group forR^(a36) include an aralkyl group such as benzyl group; an aromatichydrocarbon group having an alkyl group such as p-methylphenyl group,p-tert-butylphenyl group, tolyl group, xylyl group, cumenyl group,mesityl group and 2,6-diethylphenyl group; a 2-methyl-6-ethylphenylgroup; an aromatic hydrocarbon group having an alicyclic hydrocarbongroup such as a p-cyclohexylphenyl group and a p-adamantylphenyl group;and an aryl-cyclohexyl group.

In the formula (a1-4) R^(a32) is preferably a hydrogen atom.

a²³³ is preferably a C1-C4 alkoxy group, more preferably a methoxy groupor an ethoxy group, and still more preferably a methoxy group.

“1a” is preferably 0 or 1, and more preferably 0. R^(a34)L is preferablya hydrogen atom. R^(a35) is preferably a C1-C12 hydrocarbon group, andmore preferably a methyl group or an ethyl group.

The hydrocarbon group for R^(a36) is preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon groupor a combination thereof, and more preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group or a C7-C18 aralkyl group. The alkylgroup and the alicyclic hydrocarbon group for R^(a36) are preferablyunsubstituted. When the aromatic hydrocarbon group of R^(a36) has asubstituent, the substituent is preferably a C6-C10 aryloxy group.

Examples of the structural unit (a1-4) include those derived from themonomers described in JP2010-204646A1. Among them, the structural unitis preferably the following ones represented by formula (a1-4-1) toformula (a1-4-8), and more preferably the structural units representedby formula (a1-4-1) to formula (a1-4-5).

When the resin (A) has the structural unit (a1-4), the proportionthereof is preferably 10% by mole to 95% by mole, more preferably 15% bymole to 90% by mole, still more preferably 20% by mole to 85% by mole,further more preferably 20% by mole to 70% by mole, still further morepreferably 20% by mole to 60% by mole, based on the all the structuralunits of the resin (A) (100% by mole).

Examples of the structural unit having an acid-labile group representedby formula (2) include one represented by formula (a1-5).

In formula (a1-5), R^(a8) represents a hydrogen atom, a halogen atom, ora C1-C6 alkyl group which may have a halogen atom,

Z^(a1) represents a single bond or *—(CH₂)_(h3)—CO-L⁵⁴- in which h3represents an integer of 1 to 4 and * represents a binding position toL⁵¹,

L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent an oxygen atom or asulfur atom, and

s1 represents an integer of 1 to 3, and s1′ represents an integer of 0to 3.

Herein, the structural unit represented by formula (a1-5) is sometimesreferred to as “structural unit (a1-5)”.

Examples of halogen atoms include a fluorine atom and chlorine atom,preferably a fluorine atom.

Examples of the alkyl group which may have a halogen atom include amethyl group, an ethyl group, n-propyl group, an isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group a heptyl group, a 2-ethylhexyl group, an octyl group, afluoromethyl group, and a trifluoromethyl group.

In the formula (a1-5), R^(a8) preferably represents a hydrogen atom, amethyl group, or a trifluoromethyl group.

L⁵¹ represents preferably an oxygen atom.

It is preferred that one of L⁵² and L⁵³ represents an oxygen atom, whilethe other represents a sulfur atom.

s1 preferably represents 1. s1′ represents an integer of 0 to 2. Z^(a1)preferably represents a single bond or *—CH₂—CO—O— wherein * representsa binding position to L⁵¹.

Examples of the structural unit (a1-5) include one derived from monomermentioned in JP2010-61117A1, which preferably include the followingones.

Among them, the structural units represented by the formula (a1-5-1) and(a1-5-2) are more preferred.

When Resin (A) has a structural unit (a1-5), its content is usually 1 to50% by mole, preferably 3 to 45% by mole and more preferably 5 to 40% bymole, and still more preferably 5 to 30% by mole, based on 100% by moleof all the structural units of the resin.

Another example of the structural unit (a1) further includes thefollowing ones.

When Resin (A) has any one of these structural units, its content isusually 10 to 95% by mole, preferably 15 to 90% by mole, more preferably20 to 85% by mole, still more preferably 20 to 70% by mole, further morepreferably 20 to 60% by mole, based on 100% by mole of all thestructural units of the resin.

The structural unit (s) is derived from a monomer having no acid-labilegroup.

The structural unit (s) preferably has a hydroxy group or a lactonering.

Hereinafter, the structural unit (s) having a hydroxy group is referredto as “structural unit (a2)”, and the structural unit (s) having alactone ring is referred to as “structural unit (a3)”.

The hydroxy group which the structural unit (a2) has may be an alcoholichydroxy group or a phenolic hydroxy group.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, the resin which comprises the structural unit(a2) having a phenolic hydroxy group is preferred. When ArF excimerlaser (wavelength: 193 nm) is used as an exposure system, the resinwhich comprises the structural unit (a2) having an alcoholic hydroxygroup is preferred and the resin which comprises the structural unit(a2-1) described later is more preferred.

Resin (A) may have two or more of the structural units (a2). Examples ofthe structural unit (a2) having a phenolic hydroxy group include onerepresented by formula (a2-A):

In formula (a2-A), R^(a50) represents a hydrogen atom, a halogen atom, aC1-C6alkyl group or a C1-C6halogenated alkyl group, A^(a50) presents asingle bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)—, where * represents abinding position to the carbon atom bonded to R^(a50), A^(a52)represents a C1-C6 alkanediyl group, X^(a51) and X^(a52) represents —O—,—CO—O—, or —O—CO—, and nb represents an integer of 0 or 1, R^(a51) isindependently in each occurrence a halogen atom, a C1-C6 alkyl group, aC1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, anacryloyl group or a methacryloyl group, and mb represents an integer of0 to 4.

In the formula (a2-A), examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom or iodine atom, examples of theC1-C6 alkyl group include a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, an isobutyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group, and a C1-C4alkyl group is preferred and a C1-C2 alkyl group is more preferred and amethyl group is especially preferred.

Examples of the C1-C6 halogenated alkyl group include a trifluoromethylgroup, a pentafluoroethyl group, a heptafluoropropyl group, aheptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Examples of the C1-C6 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, an isopropoxy group, a butoxy group, anisobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxygroup and a hexyloxy group, and a C1-C4 alkoxy group is preferred and aC1-C2 alkoxy group is more preferred and a methoxy group is especiallypreferred.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group, and examples of the C2-C4 acyloxy groupinclude an acetyloxy group, a proponyloxy group and a butyryloxy group.

R^(a51) is preferably a methyl group.

R^(a50) is preferably a hydrogen atom and a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group and an ethyl group, and stillmore preferably a hydrogen atom and a methyl group.

As to A^(a50) , examples of *—Xa⁵¹-(A^(a52)-X^(a52))_(nb)— include *—O—,*—CO—O—, *—O—CO—, *—CO—O-A^(a52)-CO—O—, *—O—CO-A^(a52)-O—,*—O-A^(a52)-CO—O—, *—CO—O-A^(a52)-O—CO—, *—O—CO-A^(a52)-O—CO—,preferably *—CO—O—, *—CO—O-A^(a52)-CO—O— and *—O-A^(a52)-CO—O—.

As to A^(a52), examples of the alkanediyl group include an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a50) is preferably a single bond, *—CO—O— or *—CO—O-A^(a52)-O—CO—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—O—CO—, and stillmore preferably a single bond or *—CO—O—.

In the formula (a2-A), mb is preferably 0, 1 or 2, and is morepreferably 0 or 1, and especially preferably 0.

In formula (a2-A), a hydroxyl group on the phenyl group is positionedpreferably on o-position or p-position, and more preferably onp-position.

Examples of the structural unit (a2) include those derived from themonomers described in. JP2010-204634A1 and JP2012-12577A1. Preferredexamples of the structural unit (a2) include the structural unitsrepresented by formulae (a2-2-1) to (a2-2-4) and those represented byformulae in which a methyl group corresponding to R^(a50) has beenreplaced by a hydrogen atom.

Among them, the structural units represented by formulae (a2-2-1) and(a2-2-4) and those represented by formulae in which a methyl groupcorresponding to R^(a50) has been replaced by a hydrogen atom are morepreferred.

When Resin (A) has the structural unit represented by formula (a2-A) itscontent is usually 5 to 80% by mole and preferably 10 to 70% by mole,more preferably 15 to 65% by mole, still more preferably 10 to 70% bymole, further more preferably 15 to 65% by mole, and still further morepreferably 20 to 65% by mole, based on the sum of the structural unitsof the resin.

Examples of the structural unit (a2) having an alchoholic hydroxy groupinclude one represented by formula (a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a3) represents *—O— or *—O—(CH₂)_(k2)—CO—O— inwhich * represents a binding position to —CO—, and k2 represents aninteger of 1 to 7, and ol represents an integer of 0 to 10.

Hereinafter, the structural unit represented by formula (a2-1) isreferred to as “structural unit (a2-1)”.

In the formula (a2-1), R^(a14) is preferably a methyl group R^(a15) ispreferably a hydrogen atom. R^(a16) is preferably a hydrogen atom or ahydroxy group. L^(a3) is preferably *—O— or *—O—(CH₂)_(f2)—CO—O— inwhich * represents a binding position to —CO—, and f2 represents aninteger of 1 to 4, is more preferably *—O— and *—O—CH₂—CO—O—, and isstill more preferably *—O—, and of is preferably 0, 1, 2 or 3 and ismore preferably 0 or 1.

Examples of monomers from which the structural unit (a2-1) is derivedinclude compounds as mentioned in J72010-204646A.

Preferred examples of the structural unit (a2-1) include thoserepresented by formulae (a2-1-1) to (a2-1-6).

Among them, more preferred are the structural units represented byformulae (a2-1-1), (a2-1-2), (a2-1-3) and (a2-1-4), still more preferredare the structural units represented by formulae (a2-1-1) and (a2-1-3).

When Resin (A) has the structural unit (a2-1), its content is usually 1to 45% by mole, preferably 1 to 40% by mole, and more preferably 1 to35% by mole, still more preferably 2 to 20% by mole, further still morepreferably 2 to 10% by mole, based on the sum of the structural units ofthe resin.

Examples of the lactone ring for the structural unit (a3) include amonocyclic lactone ring such as β-propiolactone ring, γ-butyrolactonering and γ-valerolactone ring, and a condensed ring formed from amonocyclic lactone ring and the other ring. Among them, preferred areγ-butyrolactone ring and a condensed lactone ring formed fromγ-butyrolactone ring and the other ring.

Preferred examples of the structural unit (a3) include those representedby formulae (a3-1), (a3-2), (a3-3) and (a3-4).

In formulae, L^(a4), L^(a5) and L^(a6) each independently represent *—O—or *—O—(CH₂)_(k3)—CO—O— in which * represents a binding position to acarbonyl group and k3 represents an integer of 1 to 7,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a21) represents a C1-C4 monovalent aliphatic hydrocarbon group,

R^(a24) represents a hydrogen atom, a halogen atom, or a C1-C6 alkylgroup which may have a halogen atom,

R^(a22), R^(a23) and R^(a25) each independently represent a carboxylgroup, a cyano group, or a C1-C4 aliphatic hydrocarbon group,

L^(a7) represents an oxygen atom, *¹-O-L^(a8)-O—, *¹-O-L^(a8)-CO—O—,*¹-O-L^(a8)-CO—O-L^(a9)-CO—O— or *¹-O-L^(a8)-CO-O-L^(a9)-O— in whichL^(a8) and L^(a9) each independently represent C1-C6 divalent alkanediylgroup, *¹ represents a binding position to a carbonyl group,

p1 represents an integer of 0 to 5,

q1 and r1 each independently represent an integer of 0 to 3, and w1represents an integer of 0 to 8.

Examples of the aliphatic hydrocarbon group represented by R^(a21),R^(a22), R^(a23) and R^(a25) include alkyl groups such as a methylgroup, an ethyl group, a propyl group, or a butyl group.

Examples of the alkyl group represented by R^(a24) include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group,and a hexyl group, preferably a C1-C4 alkyl group, and more preferably amethyl group and an ethyl group.

Examples of halogen atom represented by R^(a24) include a fluorine atom,a chlorine atom, a bromine atom and an iodine atom.

As to R^(a24), examples of the alkyl group which has an halogen atominclude a trifluoromethyl group, a pentafluoroethyl group, aheptafluoropropyl group, a hexafluoroisopropyl group, a nonafluorobutylgroup, a nonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group, a perfluorohexyl group, a trichloromethyl group,a tribromomethyl group, and a triiodomethyl group.

As to L^(a8) and L^(a9), examples of the alkanediyl group include amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diylgroup, a butane-1,3-diyl group, 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

Preferably, L^(a4), L^(a5) and L^(a6) each independently represent *—O—or *—O—(CH₂)_(d1)—CO—O— in which * represents a binding position to —CO—and d1 represents an integer of 1 to 4. More preferably, L^(a4), L^(a5)and L^(a6) are *—O— and *—O—CH₂—CO—O—, and still more preferably L^(a4),L^(a5) and L^(a6) are *—O—.

R^(a18), L^(a19) and R^(a20) are preferably methyl groups. R^(a21) ispreferably a methyl group. Preferably, R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or amethyl group.

Preferably, p1, q1 and r1 each independently represent an integer of 0to 2, and more preferably p1, q1 and r1 each independently represent 0or 1.

L^(a24) is preferably a hydrogen atom or a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group or an ethyl group, and stillmore preferably a hydrogen atom or a methyl group.

L^(a7) represents preferably an oxygen atom or *¹—O-L^(a8)-CO—O—, morepreferably an oxygen atom, *¹—O—CH₂—CO—O— or *¹—O—C₂H₄—CO—O—.

The formula (a3-4)′ is preferably the following one.

In the formula, R^(a24) and L^(a7) are as defined above, respectively.

Examples of the monomer from which the structural unit (a3) is derivedinclude those mentioned in US2010/203446A1, US2002/098441A1 andUS2013/143157A1.

Examples of the structural unit (a3) include the following ones.

Other examples of the structural unit (a3) include those represented byformulae (a3-1) to (a3-4) in which the methyl group corresponding toR^(a18), R^(a19), R^(a20) and R^(a24) of formulae (a3-1) to (a3-4) hasbeen replaced by a hydrogen atom.

When Resin (A) has the structural unit (a3), its content thereof ispreferably 5 to 70% by mole, and more preferably 10 to 65% by mole andmore preferably 10 to 60% by mole, based oa the sum of the structuralunits of the resin.

When Resin (A) has the structural unit (a3-1), (a3-2), (a3-3) or (a3-4),its content thereof is preferably 5 to 60% by mole, and more preferably5 to 50% by mole and more preferably 10 to 50% by mole, based on the sumof the structural units of the resin.

Other examples of the structural unit (s) include a structural unithaving a fluorine atom and a structural unit which has a hydrocarbon notbeing removed therefrom by action of an acid.

Hereinafter, the structural unit (s) having a halogen atom is referredto as “structural unit (a4)”.

Halogen atoms for the structural unit (a4) may be a fluorine atom, achlorine atom, a bromine atom, or an iodine atom. The structural unit(a4) has preferably a fluorine atom.

Examples of the structural unit (a4) include the following one.

In the formula, R⁴¹ represents a hydrogen atom or a methyl group, R⁴²represents a C1-C24 saturated hydrocarbon group having a floride atom inwhich hydrocarbon group a methylene group can be replaced by an oxygenatom or a carbonyl group.

Examples of the saturated hydrocarbon group include C1-C24 chainhydrocarbon group, an alicyclic hydrocarbon group including a monocyclicor polycyclic hydrocarbon group, and any combinations of these groups.

Examples of the chain hydrocarbon group include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a decyl group, a dodecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group and an octadecylgroup.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group,decahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups:

Examples of the combinations of these groups include any combination ofan alkyl or alkanediyl group with an alicyclic hydrocarbon group, whichspecifically include -[alkanediyl group] -[alicyclic hydrocarbon group],-[alicyclic hydrocarbon group] -[alkyl group] and -[alkanediyl group]-[alicyclic hydrocarbon group] -[alkyl group].

Typical examples of the structural unit (a4) include structural unitsrepresented by formulae (a4-0), (a4-1) and (a4-4).

In the formula (a4-0) R^(5a) represents a hydrogen atom or a methylgroup, L^(4a) represents a single bond or a C1-C4 alkanediyl group,L^(3a) represents a C1-C8 perfluoroalkanediyl group, or a C3-C12perfluorocycloalkanediyl group, and R⁶⁶ represents a hydrogen atom or afluorine atom.

For L^(4a), examples of the alkanediyl group include a linear alkanediylgroup such as a methylene group, an ethylene group, a propane-1,3-diylgroup, and butane-1,4-diyl group, and a branched alkanediyl group suchas an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diylgroup, a 2-methyl propane-1,3-yl group and 2-methylpropane-1,2-diylgroup.

Examples of the perfluoroalkanediyl group for L^(3a) includedifluoromethylene, perfluoroethylene, perfluoropropane-1,3-diyl,perfluoropropane-1,2-diyl, perfluoropropane-2, 2-diyl,perfluorobutane-1,4-diyl, perfluorobutane-2,2-diyl,perfluorobutane-1,2-diyl, perflubropentane-1,5-diyl,perfluoropentane-2,2-diyl, perfluorppentane-3,3-diyl,perfluorchexane-1,6-diyl, perfluorohexane-2,2-diyl,perfluorohexane-3,3-diyl, perfluoroheptane-1,7-diyl,perfluoroheptane-2,2-diyl, perfluorpheptane-3,4-diyl,perfluorcheptane-4,4-diyl, perfluorooctan-1,8-diyl,perfluorooctane-2,2-diyl, perfluorooctan-3,3-diyl andperfluorooctane-4,4-diyl groups.

Examples of the perfluorocycloalkanediyl group for L^(3a) includeperfluorocyclohexanediyl, perfluorocyclopentanediyl,perfluorocycloheptanediyl and perfluoroadamantanediyl groups.

L^(3a) is preferably C1-C6 perfluoroalkanediyl group more preferably aC1-C3 perfluoroalkanediyl group.

L^(4a) is preferably a single bond, a methylene group or an ethylenegroup, more preferably a single bond or a methylene group.

Examples of the structural unit represented by formula (a4-0) includethe structural units represented by the following formulae and thoserepresented by the following formulae in which a methyl group has beenreplaced by a hydrogen atom.

The structural unit represented by formula (a4-11) is as follows.

In the formula, R^(a41) represents a hydrogen atom or a methyl group;

R^(a42) represents a C1-C20 saturated hydrocarbon group which may have asubstituent and in which a methylene group can be replaced by an oxygenatom or a carbonyl group, provided that each or both of A^(a41) andR^(a42) have a fluorine atom; and

A^(a44) represents a C1-C6 alkanediyl group which may have a substituentor a moiety represented by formula (a-g1):

-A^(a42)X^(a41)-A^(a43)_(s)X^(a42)-A^(a44)-   (a-g1)

in which s represents an integer of 0 to 1,

A^(a42) and A^(a44) respectively represent, a C1-C5 saturatedhydrocarbon group which may have a substituent,

A^(a43) represents a single bond or a C1-C5 chain or alicyclichydrocarbon group which may have a substituent,

X^(a41) and X^(a42) respectively represent —O—, —CO—, —CO—O—, or —O—CO—,provided that the sum of carbon atoms of A^(a42), A^(a43), A^(a44),X^(a44) and X^(a42) are each 7 or less; and

A^(a44) is bonded to —O—CO—R^(a42).

The saturated hydrocarbon group for R^(a42) includes a chain saturatedhydrocarbon group, an alicyclic hydrocarbon group including monocyclichydrocarbon group and a polycyclic hydrocarbon group, and anycombination of these hydrocarbon groups.

Examples of the chain saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a decyl group, a dodecylgroup, a hexadecyl group, a pentadecyl group, a hexyldecyl group, ahetadecyl group and an octadecyl group.

Examples of alicyclic hydrocarbon groups include cycloalkyl groups suchas a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group; and monovalent polycyclic hydrocarbon groups such as adecahyrdonaphthyl group, an adamantyl group, a norbornyl group, and thefollowing groups where * represents a bind position.

Examples of the combination of these groups include combination of analkanediyl or alkyl group with an alicyclic hydrocarbon group such as-[alkanediyl group] - [alicyclic hydrocarbon group] - [alicyclichydrocarbon group]- [alkyl group], and - [alkanediyl group] - [alicyclichydrocarbon group] - [alkyl group].

The hydrocarbon group represented by R^(a42) preferably has asubstituent. Examples of the substituent include a halogen atom and agroup represented by formula (a-g3)

—X^(a43)-A^(a45)   (a-g3)

in which X^(a43) represents an oxygen atom, a carbonyl group, acarbonyloxy group or an oxycarbonyl group, and

A^(a45) represents a C1-C17 chain or alicyclic hydrocarbon group whichmay have a fluorine atom.

Examples of the chain or alicyclic hydrocarbon group for A^(a45) includealkyl groups such as a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group, a hexyl group, a heptyl group, an octylgroup, a decyl group, a dodecyl group, a hexadecyl group, a pentadecylgroup, a hexyldecyl group, a heptadecyl group and an octadecyl group;

monocyclic alicyclic hydrocarbon groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andmonovalent polycyclic hydrocarbon groups such as a decahyrdonaphthylgroup, an adamantyl group, a norbornyl group, and the following groupswhere * represents a binding position.

R^(a42) is preferably a chain or alicyclic hydrocarbon group which mayhave a halogen atom, more preferably an alkyl group which has a halogenatom or a group represented by formula (a-g3).

If R^(a42) is a chain or alicyclic hydrocarbon group which has a halogenatom, it is preferably a chain or alicyclic hydrocarbon group which hasa fluorine atom, more preferably a perfluoroalkyl group or aperfluorocycloalkyl group, and still more preferably a C1-C6, especiallyC1-C3, perfluoroalkyl group.

Specific examples of the perfluoroalkyl group include a perfluoromethylgroup, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutylgroup, a perfluoropentyl group, a perfluorohexyl group, aperfluoroheptyl group, and a perfluorooctyl group. Specific examples ofthe perfluorocycloalkyl group include a perfluorocyclohexyl group.

Examples of the substituents for R^(a42) include a hydroxy group, aC1-C6 alkoxy group, and a halogen atom such as fluorine atom.

If R^(a42) is a chain or alicyclic hydrocarbon group which has a grouprepresented by formula (a-g3), R^(a42) has preferably 15 or less carbonatoms, more preferably 12 or less carbon atoms.

If R^(a42) has a group represented by formula. (a-g3), R^(a42) haspreferably one group represented by formula (a-g3).

The chain or alicyclic hydrocarbon group which has a group representedby formula (a-g3) is preferably a group represented by formula (a-g2):

-A^(a46)-X^(a44)-A^(a47)   (a-g2)

in which A^(a46) represents a C1-C17 chain or alicyclic hydrocarbongroup which may have a fluorine atom, X^(a44) represents a carbonyloxygroup or an oxycarbonyl group, and A^(a47) represents a C1-C17 chain oralicyclic hydrocarbon group which may have a fluorine atom, providedthat A^(a46), A^(a47) and X^(a44) have 18 or less of carbon atoms intotal and one or both of A^(a46) and A^(a47) have a fluorine atom.

The chain or alicyclic hydrocarbon group represented by A^(a46) haspreferably 1 to 6, more preferably 1 to 3 carbon atoms.

The chain or alicyclic hydrocarbon group represented by A^(a47) haspreferably 4 to 15, more preferably 5 to 12 carbon atoms. A^(a47) ismore preferably a cyclohexyl group or an adamantyl group.

Examples of the moiety represented by A^(a46)-X^(a44)-A^(a47) includethe following ones.

In each formula, * represents a binding position to a carboxy group.

Examples of A^(a41) typically include a C1-C6 alkanediyl group which maybe a linear chain or branched chain. Specific examples of them includelinear chain alkanediyl groups such as a methylene group, an ethylenegroup, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, or a hexane-1,6-diyl group; and branched chainalkanediyl groups such as a propane-1,3-diyl group, a butane-1,3-diylgroup, a 1-methylbutane-1,2-diyl group, or a 2-methylbutane-1,4-diylgroup. Examples of the substituents on the alkanediyl group include ahydroxy group or a C1-C6 alkoxy group.

A^(a41) is preferably a C1-C4 alkanediyl group, more preferably a C2-C4alkanediyl group, and still more preferably an ethylene group.

Examples of the alkanediyl group represented by A^(a42), A^(a43) andA^(a44) include a methylene group, an ethylene group, a propane-1,3-diylgroup, a butane-1,4-diyl group, a 2-methylpropandiyl group, or a2-methylbutane-1,4-diyl group. Examples of the substituents on thealkanediyl group include a hydroxy group or a C1-C6 alkoxy group.

X^(a42) represents an oxygen atom, a carbonyl group, a carbonyloxy groupor an oxycarbonyl group.

Examples of the moiety represented by formula (a-g1) where X^(a42) is anoxygen atom, a carbonyl group, a carbonyloxy group or an oxycarbonylgroup include the following ones:

in which * and ** represent binding positions, and ** represents abinding position to —O—CO—R^(a42).

Typical examples of the structural unit represented by formula (a4-1)include the structural units represented by the following formulae andthose represented by the following formulae in which a methyl groupcorresponding to R^(a41) has been replaced by a hydrogen atom.

Specific examples of the structural unit (a4-1) include a structuralunit represented by the formula (a4-2):

wherein R^(f5) represents a hydrogen atom or a methyl group,

L⁴⁴ represent a C1-C6 alkanediyl group in which a methylene group can bereplaced by —O— or —CO—, and

R^(f6) represents a C1-C20 saturated hydrocarbon group that has afluorine atom, provided that L⁴⁴ and R⁶⁶ have 2 to 21 carbon atoms intotal.

Examples of the divalent-saturated hydrocarbon group for L⁴⁴ include alinear alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diylgroups; and a branched alkanediyl group such as1-methylpropane-1,3-diyl, 2-methylpropane-1, 3-diyl,2-methylpropane-1,2-diyl, 1-methylbutane-1,4-diyl and2-methylbutane-1,4-diyl groups.

Examples of the saturated hydrocarbon group for P^(f6) include analiphatic hydrocarbon group and an aromatic hydrocarbon group. Thealiphatic hydrocarbon group includes chain and cyclic groups, and acombination thereof. The aliphatic hydrocarbon group is preferably analkyl group and a cyclic aliphatic hydrocarbon group.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and2-ethylhexyl groups.

Examples of the cyclic aliphatic hydrocarbon group include any of amonocyclic group and a polycyclic group. Examples of the monocyclicalicyclic hydrocarbon group include a cycloalkyl group such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups.Examples of the polycyclic hydrocarbon groups include decahydronaphthyl,adamantyl, 2-alkyladamantane-2-yl, 1-(adamantane-1-yl) alkane-1-yl,norbornyl, methylnorbornyl and isobornyl groups.

Examples of the saturated hydrocarbon group having, a fluorine atom forinclude an alkyl group having a fluorine atom and an alicyclichydrocarbon group having a fluorine atom.

Specific examples of an alkyl group having a fluorine atom include afluorinated alkyl group such as difluoromethyl, trifluoromethyl,1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl,perfluoroethylmethyl, 1-(trifiuoromethyl)-1,2,2,2-tetrafluoroethyl,perfluoropropyl, 1-(trifluoromethyl)-2,2,2-trifluoroethyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl, 1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodeca fluorohexyl, perfluoropentylmethyl andperfluorohexyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluorocyclohexyl andperfluoroadamantyl groups.

In the formula (a4-2), L⁴⁴ is preferably a C2-C4 alkanediyl group, andmore preferably an ethylene group.

R^(f6) is preferably a C1-C6 fluorinated alkyl group.

Examples of the structural unit represented by formula (a4-2) includeones represented by the formulae (a4-1-1) to (a4-1-11) and those inwhich a methyl group corresponding to R^(f5) has been replaced by ahydrogen atom.

Specific examples of the structural unit (a4-1) include a structuralunit represented by the formula (a4-3).

In formula, R^(f7) represents a hydrogen atom or a methyl group.

L⁵ represents a C1-C6 alkanediyl group.

A^(f13) represents a C1-C18 saturated hydrocarbon group which may have afluorine atom.

X^(f12) represents a carbonyloxy group or an oxycarbonyl group.

A^(f14) represents a C1-C17 saturated hydrocarbon group which may have afluorine atom, provided that one or both of A^(f13) and A^(f14)represents a fluorine-containing aliphatic hydrocarbon group.

Examples of the alkanediyl group for L⁵include the same ones as thosefor L^(4a).

A^(f13) further includes combined groups of chain hydrocarbon groups andalicyclic hydrocarbon groups.

As to A^(f13)the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a divalent saturated chain hydrocarbon groupwhich may have a fluorine atom, more preferably a perfluoroalkanediylgroup.

Examples of the divalent chain saturated hydrocarbon group which mayhave a fluorine atom include an alkanediyl group such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group andpentanediyl group; and a perfluoroalkanediyl group such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group andperfluoropentanediyl group.

The divalent cyclic saturated hydrocarbon group which may have afluorine atom may be a divalent monocyclic or polycyclic group.

Examples of the divalent monocyclic hydrocarbon group which may have afluorine atom include a cyclohexanediyl group and aperfluorocyclohexanediyl group.

Examples of the divalent polycyclic hydrocarbon group which may have afluorine atom include an adamantanediyl group, norbornanediyl group, anda perfluoroadamantanediyl group.

In the group represented by A^(f14), the aliphatic hydrocarbon groupincludes chain saturated hydrocarbon groups, cyclic saturatedhydrocarbon groups and combined groups of these saturated hydrocarbongroups.

As to A^(f14), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a saturated aliphatic hydrocarbon group withmay have a fluorine atom, more preferably a perfluoroalkyl group.

Examples of the chain hydrocarbon group which may have a fluorine atominclude a trifluoromethyl group, a fluoromethyl group, a methyl group, aperfluoroethyl group, a 2,2,2-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutylgroup, 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group, a heptyl group, aperfluoroheptyl group, an octyl group and a perfluorooctyl group.

The alicyclic hydrocarbon group which may have a fluorine atom may bemonocyclic or polycyclic group.

Examples of the monovalent monocyclic hydrocarbon group which may have afluorine atom include a cyclopropyl group, a cyclopentyl group, acyclohexyl group, and a perfluorocyclohexyl group.

Examples of the polycyclic hydrocarbon group which may have a fluorineatom include an adamantyl group, a norbornyl group, and aperfluoroadamantyl group.

Examples of the combined groups of the above-mentioned chain andalicyclic hydrocarbon groups include a cyclopropylmethyl group, acyclobutylmethyl group, an adamantylmethyl group, a norbornylmethylgroup and a perfluoroadamantylmethyl group.

In formula (a4-3), L⁵ is preferably an ethylene group.

The chain or alicyclic hydrocarbon group represented by A^(f13) haspreferably 6 or less, more preferably 2 to 3, carbon atoms.

The chain or alicyclic hydrocarbon group represented by A^(f14) haspreferably 3 to 12, more preferably 3 to 10, carbon atoms.

A^(f14) has preferably a C3-C12 alicyclic hydrocarbon group, morepreferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexylgroup, a norbornyl group or an adamantyl group.

Examples of the structural unit represented by formula (a4-3) includepreferably those represented by the he formulae (a4-1 -1) to (a4-1′-11)and those in which a methyl group corresponding to R^(f7) has beenreplaced by a hydrogen atom.

The structural unit represented by formula (a4-4) is as follows.

In formula (a4-4), R^(f21) represents a hydrogen atom or a methyl group;

A^(f21) represents —(CH₂)_(j1), —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O—(CH₂)_(j5)— where j1, j2, j3, j4 or j5 eachindependently represent an integer of 1 to 6; and

R^(f22) represents a C1-C10 hydrocarbon group having a fluorine atom.

R^(f22) is preferably a C1-C10 alkyl group having a fluorine atom or aC3-C10 alicyclic hydrocarbon group having a fluorine atom, morepreferably a C1-C10 alkyl group having a fluorine atom, and still morepreferably a C1-C6 alkyl group having a fluorine atom.

In formula (a4-4), A_(f21) is preferably —(CH₂)_(j1)—, more preferably amethylene or ethylene group, and still more preferably a methylenegroup.

Examples of the structural unit represented by formula (a4-4) includepreferably the following ones and those represented by the followingformulae in which the methyl group corresponding to R^(f21) has beenreplaced by a hydrogen atom.

When Resin (A) has the structural unit (a4), its content is preferably 1to 20% by mole, more preferably 2 to 15% by mole and still morepreferably 3 to 10% by mole based on 100% by mole of all the structuralunits of the resin.

Other examples of the structural unit (s) include one having anacid-stable hydrocarbon group. The structural unit (s) having anacid-stable hydrocarbon group is sometimes referred to as “structuralunit (a5)”.

Herein, the term “acid-stable hydrocarbon group” means such ahydrocarbon group that is not removed from the structural unit havingthe group by action of an acid generated from an acid generator asdescribed above.

The acid-stable hydrocarbon group may be a linear, branched or cyclichydrocarbon group.

The structural unit which has a hydrocarbon not being removed therefromby action of an acid may have a linear, branched or cyclic hydrocarbon,preferably an alicyclic hydrocarbon group.

Examples of the structural unit having an acid-stable hydrocarbon groupinclude one represented by formula (a5-1):

where R⁵¹ represents a hydrogen atom or a methyl group;

P⁵² represents a C3-C18monovalent alicyclic hydrocarbon group which mayhave a C1-C8 monovalent aliphatic hydrocarbon group as a substituent,provided that the alicyclic hydrocarbon group has no substituent on thecarbon atom bonded to L⁵⁵; and

L⁵⁵represents a single bond or a C1-C18divalent saturated hydrocarbongroup where a methylene group can be replaced by an oxygen atom orcarbonyl group.

The alicyclic hydrocarbon group represented by R⁵² may be a monocyclicor a polycyclic one

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon group such as a C3-C18 cycloalkyl group (e.g. a cyclopropylgroup, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group) anda polycyclic alicyclic hydrocarbon group such as an adamantyl group, ora norbornyl group.

Examples of the aliphatic hydrocarbon group include an alkyl groups suchas a methyl group, an ethyl group, n-propyl group, isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, an octyl group and 2-ethylhexyl group.

Examples of the alicyclic hydrocarbon group having a substituent includea 3-hydroxyadamantyl group, and a 3-methyladamantyl group.

R⁵² is preferably a C3-C18 unsubstituted alicyclic hydrocarbon group,more preferably an adamantyl group, a norbornyl group or a cyclohexylgroup.

Examples of the divalent saturated hydrocarbon group represented by L³³include divalent aliphatic hydrocarbon groups and divalent alicyclichydrocarbon groups, preferably divalent aliphatic hydrocarbon groups.

Examples of divalent aliphatic hydrogencarbon groups include alkanediylgroups such as a methylene group, an ethylene group, a propanediylgroup, a butanediyl group and a pentanediyl group.

The divalent alicyclic hydrocarbon groups may be monocyclic orpolycyclic one.

Examples of divalent monocyclic hydrocarbon groups includecycloalkanediyl groups such as a cyclopentanediyl group and acyclohexanediyl group. Examples of divalent polycyclic alicyclichydrocarbon groups include an adamantanediyl group and a norbornanediylgroup.

Examples of the divalent hydrocarbon group where a methylene group hasbeen replaced by an oxygen atom or carbonyl group include thoserepresented by formulae (L1-1) to (L1-4).

In these formulae, * represents a binding position to an oxygen atom.

X^(x1) is carbonyloxy group or an oxycarbonyl group; and

L^(x1) is a C1-C16 divalent aliphatic saturated hydrocarbon group, andL^(x2) is a single bond or a C1-C15 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x1) and L^(x2) is 16 or less.

L^(x3) is a C1-C17 divalent aliphatic saturated hydrocarbon group, andL^(x4) is a single bond or a C1-C16 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x3) and L^(x4) is 17 or less.

L^(x5) is a C1-C15 divalent aliphatic saturated hydrocarbon group, andL_(x6) and L^(x7) are a single bond or a C1-C14 divalent chain oralicyclic hydrocarbon group, provided that the total number of thecarbon atoms in L^(x5), L^(x6) and L^(x7) is 15 or less.

L^(x8) and L^(x9) are each independently a single bond or a C1-C12divalent chain or alicyclic hydrocarbon group, and W^(x1) is a C3-C15divalent cyclic saturated hydrocarbon group, provided that the totalnumber of the carbon atoms in L^(x8), L^(x9) and W^(x1) is 15 or less.

L^(x1) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x2) is preferably a single bond, or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond.

L^(x3) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x4) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond, a methylenegroup or an ethylene group.

L^(x5) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x6) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a methylene group or anethylene group.

L^(x7) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a methylene group or anethylene group.

L^(x8) is preferably a single bond or a C1-C8divalent aliphaticsaturated hydrocarbon group, more preferably a single bond or amethylene group.

L^(x9) is preferably a single bond or a C1-C8divalent aliphaticsaturated hydrocarbon group, more preferably a single bond or amethylene group.

W^(x1) is a preferably C3-C10 divalent cyclic saturated hydrocarbongroup, more preferably a cyclohexanediyl group or an adamantanediylgroup.

Examples of the group represented by formula (L1-1) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-2) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-3) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-4) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

L is preferably a single bond or a group represented by formula (L1-1).

Examples of the structural unit represented by formula (a5-1) includethe following ones and those where a methyl group has been replaced by ahydrogen atom in each formula.

When Resin (A) has the structural unit (a5), its content is preferably 1to 30% by mole, more preferably 2 to 20% by mole and still morepreferably 3 to 15% by mole based on 100% by mole of all the structuralunits of the resin.

<Structural Unit (II)>

Resin (A) may comprise a structural unit decomposed by irradiation togenerate an acid. Said structural unit is referred to as “the structuralunit (II)”. Examples of the structural unit (II) include one asdescribed in JP2016-79235A1.

The structural unit (II) preferably comprises a sulfonate or carboxylategroup and an organic cation, or a S⁺ group and an organic anion at itsside chain.

The structural unit (II) which comprises a sulfonate or carboxylategroup and an organic cation at its side chain is preferably representedby formula (II-2-A′):

wherein X^(III3) represents a C1-C18 divalent saturated hydrocarbongroup in which a methylene group can be replaced by —O—, —S— or —CO— andin which a hydrogen atom can be replaced by a fluorine atom, a hydroxylgroup or a C1-C6 alkyl group which may have a fluorine atom,

A^(x1) represents a C1-C8 alkanediyl group in which a hydrogen atom canbe replaced by a fluorine atom or a C1-C6 perfluoroalkyl group, RA⁻represents a sulfonate or carboxylate group,

R^(III3) represents a hydrogen atom, a halogen atom or a C1-C6 alkylgroup in which a hydrogen atom can be replaced by a halogen atom, andZA⁺ represents an organic cation.

For R^(III3), examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

For R^(III3), examples of a halogen-containing alkyl group include aperfluoromethyl group and a perfluoroethyl group.

For A^(X1), examples of the alkanediyl group include a methylene group,an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, an ethane-1,1-diylgroup, a propane-1,1-diyl group, a propane-1,2-diyl group, apropane-2,2-diyl group, a pentane-2,4-diyl group, a2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group,pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group.

For X^(III3), examples of divalent aliphatic hydrocarbon group include alinear alkanediyl group, a branched alkanediyl group, a monocyclicalicyclic hydrocarbon, a polycyclic alicyclic hydrocarbon, and anycombinations of these groups, specific examples of which include alinear alkanediyl group such as a methylene group, an ethylene group, apropane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diylgroup, a pentane-1,5-diyl group, a hexane-1,6-diyl group, aheptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diylgroup, a decane-1,10-diyl group, an undecane-1,11-diyl group, adodecane-1,12-diyl group;

a branched alkanediyl group such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group;

cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and divalent polycyclic alicyclichydrocarbon groups such as norbornane-1,4-diyl group,norbornane-2,5-diyl group, adamantane-1,5-diyl group, andadamantane-2,6-diyl group.

Examples of the saturated hydrocarbon group in which a methylene grouphas been replaced by —O—, —S— or —CO— include divalent groupsrepresented by the formulae (X1) to (X53).

In each formula, X³ represents a C1-C16 divalent hydrocarbon group, X⁴represents a C1-C15 divalent hydrocarbon group, X⁵ represents a C1-C13divalent hydrocarbon group, X⁶ represents a C1-C14 divalent hydrocarbongroup, X⁷ represents a C1-C14 divalent hydrocarbon group, and X⁸represents a C1-C12 divalent hydrocarbon group and * represents abinding position to A^(x1), provided that each divalent grouprepresented. by one of formulae (X1) to (X53) has 1 to 17 carbon atomsin total.

Examples of the organic cation represented by ZA⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation.

Among them, an organic self odium cation and an organic iodonium cationare preferred, and a sulfonium cation, specifically an arylsulfoniumcation, is more preferred.

The structural unit represented by formula (II-2-A′) is preferablyrepresented by formula (II-2-A) :

wherein X^(III3), R^(III3) and ZA⁺ are as defined above;

R^(III2) and R^(III4) each independently represent a hydrogen atom, afluorine atom or a C1-C6 perfluoroalkyl group;

z2A represents an integer of 0 to 6; and

Q^(a) and Q^(b) each independently represent a fluorine atom or a C1-C6perfluoroalkyl group.

For Q^(a), Q^(b), R^(III2) and R^(III4), examples of a perfluoroalkylgroup include a trifluoromethyl group, a pentafluoroethyl group, aheptafluoropropyl group, a nonafluorobutyl group, an undecafluoropentylgroup and a tridecafluorohexyl group, and a trifluoromethyl group ispreferred.

The structural unit represented by formula (II-2-A) is preferablyrepresented by formula (II-2-A-1):

wherein R^(III2), R^(III3), R^(III4), Q^(a), Q^(b), z2A and ZA⁺ are asdefined above;

R^(III5) represents a C1-C12 saturated hydrocarbon group, and

X^(I2) represents a C1-C18 divalent saturated hydrocarbon group in whicha methylene group can be replaced by —O—, —S— or —CO— and in which ahydrogen atom can be replaced by a halogen atom or a hydroxyl group.

For R^(III5), examples of the saturated hydrocarbon group include chainalkyl groups such as methyl group, an ethyl group, a propyl group, anisopropyl group, a butyl group, a sec-butyl group, a tent-butyl group, apentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group and adodecyl group.

For X^(I2), examples of the divalent saturated hydrocarbon group includethe same examples as the divalent saturated hydrocarbon group forX^(III3).

The structural unit represented by formula (II-2-A-1) is preferablyrepresented by formula (II-2-A-2):

wherein R^(III3), R^(III5), and ZA⁺ are as defined above; and

n and m each independently represent 1 or 2,

Examples of the structural unit represented by formula (II-2-A′) includethe following ones and those recited in WO2012/050015A1.

The structural unit (II) which comprises a S⁺ group and an organic anionat its side chain is preferably represented by formula (II-1-1) :

Where A^(II1) represents a single bond or a divalent connecting group,

R^(II1) represents a C6-C18 divalent aromatic hydrocarbon group,

R^(II2) and R^(II3) each independently represent a C1-C18 hydrocarbongroup or jointly represents a ring structure together S⁺ bonded thereto,

R^(II4) represents a hydrogen atom, a halogen atom or a C1-C6 alkylgroup in which a hydrogen atom can be replaced by a halogen atom, and A⁻represents an organic anion.

For R^(II1), examples of the aromatic hydrocarbon group include aphenylene group and naphthylene group.

For R^(II2) and R^(II3), examples of the hydrocarbon group include thealkyl groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groupsand any combination of these groups.

For R^(II4), examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

For R^(II4), examples of a halogen-containing alkyl group include aperfluoromethyl group and a perfluoroethyl group.

For A^(II1), examples of the divalent connecting group include a C1-C18divalent saturated hydrocarbon group in which a methylene group can bereplaced by —O—, —S— or —CO—. Specific examples of the divalentconnecting group include the same saturated hydrocarbon grouprepresented by X^(III3).

Examples of cation of the structural unit represented by formula(II-1-1) include the following ones.

Examples of the organic anion represented by A⁻ include a sulfonateanion, a sulfonylimide anion, a sulfonylmethide anion and a carboxylateanion.

Among them, a sulfonate anion is preferred. For A⁻, a sulfonate anion ispreferably the same one as used for the salt represented by formula(B1).

For A⁻, examples of a sulfonylimide anion include the following ones.

For A⁻, examples of a sulfonylmethide anion include the following ones.

For A⁻, examples of a carbonyloxy anion include the following ones.

Examples of the structural unit represented by formula (II-1-1) includethe following ones.

When Resin (A) has the structural unit (II), its content is preferably 1to 20% by mole, more preferably 2 to 15% by mole, still more preferably3to 10% by mole, based on100% by mole of all t structural units of theresin.

Resin (A) is preferably one which consists of a structural unit (a1) anda structural unit (s).

The structural unit (a1) is preferably one selected from the groupconsisting of the structural unit (a1-0), the structural unit (a1-1) andthe structural unit (a1-2), particularly that is one having a cyclohexylgroup or a cyclopentyl group. More preferably, Resin (A) has twostructural units selected from the group consisting of the structuralunit (a1-0), the structural unit (a1-1) and the structural unit (a1-2),particularly that is one having a cyclohexyl group or a cyclopentylgroup.

The structural unit (s) is preferably one selected from the groupconsisting of the structural unit (a2) and the structural unit (a3). Thestructural unit (a2) is preferably the structural unit (a2-A) or (a2-1).The structural unit (a3) is preferably the structural unit (a3-1)structural unit (a3-2) and the structural unit (a3-4).

Resin (A) can be produced according to known polymerization methods suchas radical polymerization.

The resin has usually 2,000 or more of the weight-average molecularweight, preferably 2,500 or more of the weight-average molecular weight,more preferably 3,000 or more of the weight-average molecular weight.The resin has usually 50,000 or less of the weight-average molecularweight, more preferably 30,000 or less of the weight-average molecularweight, and more preferably 15,000 or less of the weight-averagemolecular weight.

The weight-average molecular weight can be measured with gel permeationchromatography.

The composition of the present disclosure may have another resin thanResin (A).

Another resin than Resin (A) comprises no structural unit (a1).

Another resin than Resin (A) may comprise the structural unit (a2), thestructural unit (a3), the structural unit (a4) and the structural unit(a5).

Examples of another resin than Resin include one which comprises thestructural unit (a4) or which consists of the structural unit (a4) andthe structural unit (a5) [these resins are collectively referred to as“Resin (X)”].

In Resin (X), the content of the structural unit (a4) is preferably 30%by mole or more, more preferably 40% by mole or more, still morepreferably 45% by mole or more based on the sum of the structural unitsin the resin.

Resin (X) usually has 6000 or more of the weight-average molecularweight, preferably 7000 or more of the weight-average molecular weight.The resin usually has 80,000 or less of the weight-average molecularweight, preferably has 60,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with known methodssuch as liquid chromatography or gas chromatography.

When the photoresist composition contains Resin (X), the content of theresin is preferably 1 to 60 weight parts, more preferably 1 to 50 weightparts, and still more preferably 1 to 40 weight parts, further morepreferably 1 to 30 weight parts, further still more preferably 1 to 8weight parts, relative to 100 parts of Resin. (A).

The total content of the resins in the photoresist composition of thepresent invention is usually 80% by mass or more, preferably 90% by massor more, based on the sum of solid components, and usually 99% by massor less based on the sum of solid components. In this specification,“solid component” means components other than a solvent in thephotoresist composition.

The resin can be obtained by conducting polymerization reaction of thecorresponding monomer or monomers. The polymerization reaction isusually carried out in the presence of a radical initiator. Thispolymerization reaction can be conducted according to known methods.

<Solvent>

Preferably, the photoresist composition of the disclosure furthercontains a solvent.

The amount of the solvent is usually 90% by woightor more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the present invention. Theamount of the solvent is usually 99.9% by weight or less and preferably99% by weight or less based on total amount of the photoresistcomposition of the present invention. The content can be measured withknown methods such as liquid chromatography or gas chromatography.

Examples of the solvent include a glycol ether ester such as ethylcellosolve acetate, methyl cellosolve acetate and propylene glycolmonomethyl ether acetate; a glycol ether such as propylene glycolmonomethyl ether; an ester such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; a ketone such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and a cyclic ester such asγ-butyxolactone.

<Quencher>

The photoresist composition of the disclosure may further contain aquencher such as a basic compound. The “quencher”has the property thatit can trap an acid, especially an acid generated from the acidgenerator by exposure to light for lithography.

Examples of the quencher include a basic compound, such as a basicnitrogen-containing organic compound, and a salt which generates an acidhaving acidity weaker than an acid generated from the acid generators.

Examples of the basic nitrogen-containing organic compound include anamine compound such as an aliphatic amine, an aromatic amine andammonium salt. Examples of the aliphatic amine include a primary amine,a secondary amine and a tertiary amine. Examples of the aromatic amineinclude an aromatic amine.

Examples of the quencher include 1-naphthylamine, 2-naphthylamine,aniline, diisopropylaniline, 2-,3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,pentylamine, doctylamine, triethylamine, trimethylamine, tripropylamine,tributylamine, tripentylamine, trihexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, methyldibutylamine,methyldipentylamine, methylddhexylamine, methylcyclohexylidene,methyldiheptylamine, methyldioctylamine, methyldinonylamine,methyldidecylamine, ethyldibutylamine, ethyldipentylamine,ethyldihexylamine, ethyldiheptylamine, ethyldioctyiamine,ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine, tris[2-(2-methoxvethoxy)ethyl]amine, triisopropanolamine, ethylenediamine,tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, piperazine, morpholine,piperidine, hindered amine compound having a piperidine structure,2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine,4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone,4,4′-dipyridylsulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the quaternary ammonium hydroxide includetetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

As to salt which generates an acid having acidity weaker than an acidgenerated from the acid generators, the acidity in the salts is shown bythe acid dissociation constant (pKa).

The acid dissociation constant of acid generated from the salt for aquencher is usually −3<pKa.

The salt for a quencher is preferably a salt of −1<pKa<7, and morepreferably a salt of 0<pKa<5.

Specific examples of the salt for a quencher include the following ones,an onium carboxylic acid salt such as the salt of formula (D), and saltsrecited in US2012/328986A1,US2011/171576A1, US2011/201823A1,JP2011-39502A1, and US2011/200935A1.

The photoresist composition comprises onium carboxylic acid salt, morepreferably the salt of formula (D).

In formula (D) R^(D1) and R^(D2) respectively represent a C1-C1.2monovalent hydrocarbon group, a C1-C6 alkoxy group, a C2-C7 acyl group,a C2-C7 acyloxy group, a C2-C7 alkoxycarbonyl group, a nitro group or ahalogen atom. The symbols m′ and n′ each independently represent aninteger of 0 to 4, preferably an integer of 0 to 2, more preferably 0.

Examples of the compounds represented by formula (D) include thefollowing ones.

The content of quencher is preferably 0.01 to 5% by mass, morepreferably 0.01 to 4% by mass, still more preferably 0.01 to 3% by mass,and further more preferably 0.01 to 1% by mass, based on sum of solidcomponent.

The photoresist compositions of the present invention may comprise, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist compositions of the present invention can be prepared bymixing, usually in a solvent, an acid generator which contains the salt(I) and Resin (A) and if necessary a quencher, and/or additives at asuitable ratio for the composition, optionally followed by filtratingthe mixture with a filter having 0.003 μm to 0.2 μm of a pore size.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like. The mixing timeis usually 0.5 to 24 hours, which can be selected in view of thetemperature. The means for mixing the components is not limited tospecific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the presentinvention on a substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Examplesof the substrate include a silicon wafer or a quartz wafer on which asensor, a circuit, a transistor or the like is formed.

The formation of the composition film is usually conducted using aheating apparatus such as hot plate or a decompressor, and the heatingtemperature usually 50 to200° C. When the pressure is reduced duringheating, the operation pressure is usually 1 to 1.0*10⁵ Pa. The heatingtime is usually 10 to 180 seconds.

The composition film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F₂ laser (wavelength: 157 nm),a light source radiating harmonic laser light in a far UV region or avacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser), and a lightsource radiating electron beam or EUV (extreme ultraviolet) light.

The temperature of baking of the exposed composition film is usually 50to 200° C., and preferably 70 to 150° C.

The development of the baked composition film is usually carried outusing a development apparatus. The development method includes dippingmethods, paddle methods, spray methods and dynamic dispense method. Thedeveloping temperature is preferably 5 to 60° C., and the developingtime is preferably 5 to 300 seconds.

The positive and negative type photoresist patterns can be obtained bythe development depending on a developer to be used therefor.

When a positive type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with an alkaline developer. The alkali developer to be usedmay be any one of various alkaline aqueous solution used in the art.Generally, an aqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. The alkaline developer may comprise asurfactant.

After development, the photoresist film having photoresist pattern ispreferably washed with ultrapure water, and the remained water on thephotoresist film and the substrate is preferably removed therefrom.

When a negative type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with a developer containing an organic solvent, such developeris sometimes referred to as “organic developer”.

Examples of an organic solvent for organic developer include ketonesolvents such as 2-hexanone, 2-heptanone; glycolether ester solventssuch as propyleneglycolmonomethylether acetate; ester solvents such asbutyl acetate; glycolether solvents such aspropyleneglycolmpnomethylether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of organic solvent is preferably from 90% to 100% by weight,morepreferablyfrom95% to 100% by weight, in an organic developer.Preferred is that the organic developer essentially consists of anorganic solvent.

Among them, the organic developer is preferably a developer comprisingbutyl acetate and/or 2-heptanone.

The total content of butyl acetate and 2-heptanone is preferably from90% to 100% by weight, more preferably from 95% to 100% by weight.Preferred is that the organic developer essentially consists of butylacetate and/or 2-heptanone.

The organic developer may comprise a surfactant or a very small amountof water.

Development with an organic developer can be stopped by replacing thedeveloper by other solvent than it such as alcohol.

The photoresist composition of the present invention is suitable for KrFexcimer laser lithography, ArF excimer laser lithography, EUV (extremeultraviolet) lithography, EUV immersion lithography and EB (electronbeam) lithography.

EXAMPLES

The present invention will be described more specifically by Examples,which are not construed to limit the scope of the present invention.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatographyunder the following conditions.

Column: HLC-8120GPCH Type (Three Columns with guard column), TSKgelMultipore HXL-M, manufactured by TOSOH CORPORATION

Solvent: Tetrahydrofuran, Flow rate: 1.0 mL/min.

Detector: RI detector

Column temperature: 40° C.

Injection volume: 100 μL

Standard reference material: Standard polystyrene

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.).

Example 1

In a reactor, 5 parts of the salt represented by the formula (I-1-a), 15parts of dimethylformamide and 1.51 parts of triethylamine were mixedand stirred at 23° C. for 30 minutes. Into the obtained mixture, 1.62parts of the compound represented by formula (I -1-b) was dropped andthen stirred at 23° C. for 3 hours.

To the obtained reaction mixture, 50 parts of chloroform and 70 parts ofion-exchanged water were added and then stirred at 23° C. for 30minutes. Then the obtained organic layer was collected therefrom. To theobtained organic layer, 70 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes. Then the obtained organic layerwas collected therefrom. The organic layer was washed with water in theabove-mentioned manner four times.

Then the resultant mixture was concentrated. To the concentrates, 3parts of acetonitrile, 27 parts of ethyl acetate and 68 parts oftert-butylmethylether were added, and then stirred at 23° C. for 30minutes, followed by being filtrated to give 3.29 parts of the saltrepresented by formula (I-1).

MASS (ESI(+), spectrum): M⁺ 263.1

MASS (ESI(−), spectrum): M⁻ 411.1

Examples 2

In a reactor, 6.73 parts of the salt represented by the formula) (I-2-a)15 parts of dimethylformamide and 1.51 parts of triethylamine were mixedand stirred at 23° C. for 30 minutes. Into the obtained mixture, 1.62parts of the compound represented by formula (I-1-b) was dropped andthen stirred at 23° C. for 3 hours.

To the obtained reaction mixture, 50 parts of chloroform and 70 parts ofion-exchanged water were added and then starred at 23° C. for 30minutes. Then the obtained organic layer was collected therefrom. To theobtained organic layer, 70 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes. Then the obtained organic layerwas collected therefrom. The organic layer was washed with water in theabove-mentioned manner four times.

Then the resultant mixture was concentrated. To the concentrates, 30parts of tert-butylmethylether were added, and then stirred at 23° C.for 30 minutes, followed by removing its supernatant. The residues wasconcentrated to give 4.81 parts of the salt represented by formula(I-2).

MASS (ESI(+), spectrum) M⁺ 263.1

MASS (EST(−), spectrum) M⁻ 619.2

Example 3

In a reactor, 5 parts of the salt represented by the formula (I-3-a), 15parts of dimethylformamide and 1.51 parts of triethylamine were mixedand stirred at 23° C. for 30 minutes. Into the obtained mixture, 1.62parts of the compound represented by formula (I-1-b) was dropped andthen stirred at 23° C. for 3 hours.

To the obtained reaction mixture, 50 parts of chloroform and 70 parts ofion-exchanged water were added and then stirred at 23° C. for 30minutes. Then the obtained organic layer was collected therefrom. To theobtained organic layer, 70 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes. Then the obtained organic layerwas collected therefrom. The organic layer was washed with water in theabove-mentioned manner four times.

Then the resultant mixture was concentrated. To the obtained residue, 30parts of tart-butylmethylether was added and the resultant mixture wasstirred at 23° C. for 30 minutes, and then its supernatant was removedtherefrom. The obtained residue was concentrated to obtain 3.44 parts ofthe salt represented by formula (I-3).

MASS (ESI(+), spectrum): M⁺ 263.1

-   MASS (ESI(−), spectrum): M⁻ 411.1

Example 4

In a reactor, 10 parts of the salt represented by the formula (I-1-a),21.58 parts of methyl imidazole and 18 parts of iodine were mixed andstirred at 23° C. for 30 minutes. To the obtained mixture, 2.75 parts ofthe compound represented by formula (1-99-b) was added, and then stirredat 23° C. for 3 hours.

To the obtained reaction mixture, 100 parts of chloroform and 16 partsof acetic acid were added and then stirred at 23° C. for 30 minutes. Tothe obtained reaction solution, 50 parts of an aqueous saturated sodiumsulfate solution was added and stirred at 23° C. for 30 minutes. Thenthe obtained organic layer was collected therefrom.

To the obtained organic layer, 50 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes. Then the obtainedorganic layer was collected therefrom. The organic layer was washed withwater in the above-mentioned manner three times.

To the obtained organic layer, 200 parts of 5% aqueous oxalic acid wasadded, and the mixture was stirred at 23° C. for 30 minutes. Then theobtained organic layer was collected therefrom. The organic layer waswashed in the above-mentioned manner three times.

Then the resultant mixture was concentrated. To the obtained residue, 3parts of acetonitrile and 47 parts of tert-butylmethylether were addedand the resultant mixture was stirred at 23° C. for 30 minutes, followedby being filtrated to give 8.58 parts of the salt represented by formula(I-99).

MASS (ESI(+), spectrum): M⁺ 263.1

MASS (ESI(−), spectrum): M⁻ 453.2

Example 5

In a reactor, 10 parts of the salt represented by the formula (I-1-a),21.58 parts of methyl imidazole and 25.27 parts of iodine were mixed andstirred at 23° C. for 30 minutes. To the obtained mixture, 5.02 parts ofthe compound represented by formula (I-103-b) was added, and thenstirred at 23° C. for 3 hours.

To the obtained reaction mixture, 100 parts of chloroform and 16 partsof acetic acid were added and then stirred at 23° C. for 30 minutes. Tothe obtained reaction solution, 50 parts of an aqueous saturated sodiumsulfate solution was added and stirred at 23° C. Then the obtainedorganic layer was collected therefrom.

To the obtained organic layer, 50 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes. Then the obtainedorganic layer was collected therefrom. The organic layer was washed withwater in the above-mentioned manner three times.

To the obtained organic layer, 200 parts of 5% aqueous oxalic acid wasadded, and the mixture was stirred at 23° C. for 30 minutes. Then theobtained organic layer was collected therefrom. The organic layer waswashed in the above-mentioned manner three times.

Then the resultant mixture was concentrated. To the obtained residue, 1parts of acetonitrile, 20 parts of ethyl acetate and 50 parts ofteat-butylmethylether were added and the resultant mixture was stirredat 23° C. for 30 minutes, followed by being filtrated to give 8.58 partsof the salt represented by formula (I-103).

MASS (ESI(+), spectrum): M⁺ 263.1

MASS (ESI(−), spectrum): M⁻ 577.2

Example 6

In a reactor, 1.5 parts of the compound represented by the formula(I-197-a), 15 parts of dimethylformamide, 0.52 parts of potassiumcarbonate and 0.31 part of potassium iodide were mixed and stirred at23° C. for 30 minutes. To the obtained mixture, 1.92 parts of thecompound represented by formula (1-197-b) was added, and then stirred at80° C. for 2 hours. The obtained mixture was cooled to 23° C., and then30 parts of chloroform and 10 parts of ion-exchanged water were addedand then stirred at 23° C. for 30 minutes.

To the obtained organic layer, 30 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes. Then the organic layerwas collected therefrom. The organic layer was washed with water in theabove-mentioned manner three times. Then the resultant organic layer wasconcentrated to give 2.73 parts of the compound represented by formula(I-197-c).

In a reactor, 1.39 parts of the salt represented by the formula(I-197-d) and 100 parts of chloroform were mixed and stirred at 23° C.for 30 minutes.

To the obtained mixture, 0.66 parts of the compound represented byformula (I-197-e) was added and then stirred at 50° C. for 2 hours.

Then to the obtained mixture 1.18 parts of the compound represented byformula (I-197-c) was added and then stirred at 50° C. for 10 hours,followed by being cooled to 23° C.

To the obtained reaction mixture, 30 parts of chloroform and 30 parts of5% aqueous oxalic acid solution were added and then stirred at 23° C.for 30 minutes, followed by being separated into the obtained organiclayer therefrom.

To the obtained organic layer, 25 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes. Then the obtainedorganic layer was collected therefrom. The organic layer was washed withwater in the above-mentioned manner four times.

The obtained organic layer was filtrated and then the filtrates wereconcentrated. To the obtained residue, 30 parts of tert-butylmethyletherwas added and the resultant mixture was stirred at 23° C. for 30minutes, and then its supernatant was removed therefrom. The obtainedresidue was concentrated to obtain 0.68 parts of the salt represented byformula (I-197).

MASS (ESI(+), spectrum): M⁺ 263.1

MASS (EST(−), spectrum): M⁺ 527.0

Synthesis of Resin

Monomers used in the following synthesis example are shown as follow.

Those monomers are sometimes referred to as “Monomer (X)” in which (X)represents the sign of the formula corresponding to the monomer. Forexample, the monomer represented by formula (a1-1-2) is referred to as“Monomer (a1-1-2)”.

Synthesis Example 1

To the monomers (a1-1-2), (a1-2-5), (a2-1-1) and (a3-1-1) mixed in amolar ratio of 5/42/32/21 (monomer (a1-1-2)/monomer (a1-2-5)/monomer(a2-1-1)/monomer (a3-1-1)), propyleneglycolmonomethylether acetate wasadded in twice amount [based on mass] of the total parts of all monomersto prepare a mixture. To the mixture, azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were added as an initiator in a ratio of 1mol % and 3 mole % respectively based on all monomer molar amount, andthe obtained mixture was heated at 75° C. for about 5 hours.

The reaction mixture as obtained was poured into a large amount of amixture of methanol and water to precipitate resin, followed by beingfiltrated.

Then the filtrates as obtained were dissolved inpropyleneglycolmonomethylether acetate and then the solution of thefiltrates was poured into a mixture of methanol and water toreprecipitate resin. The reprecipitation step was conducted twice. As aresult, a polymer having a weight-average molecular weight of about9,100 was obtained in a yield of 97%. The polymer had the followingstructural units. That polymer is referred to as resin A1.

Resin Synthesis Example 2

To the monomer (a4-1-4), methylisobutylketone was added in 1.2 timesamount of the total parts of all monomers to prepare a solution To thesolution, azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile)were added as an initiator in a ratio of 0.7 mol % and 2.1 mole %respectively based on all monomer molar amount, and the obtained mixturewas heated at 75° C. for about 5 hours.

The reaction mixture as obtained was poured into a large amount of amixture of methanol and water to precipitate resin, followed by beingfiltrated. Repulping filtrates was conducted with a mixture of methanoland water and then the repulped filtrates was filtrated.

As a result, a polymer having a weight-average molecular weight of about17,000 was obtained in a yield of 76%. The polymer had the followingstructural unit. That polymer is referred to as resin X1.

Examples 7 to 14 and Comparative Examples 1 to 3

<Producing Photoresist Compositions>

The following components as listed in the following table were mixed anddissolved in the solvent as mentioned below, and then filtrated througha fluorine resin filter having pore diameter of 0.2 μm, to preparephotoresist compositions.

TABLE 8 Resin Acid generator Salt (I) Quencher PB (kind/ (kind/ (kind/(kind/ (° C.)/ Comp. amount amount amount amount PEB No. (part)) (part))(part)) (part)) (° C.) 1  X1/0.4 B1-21/0.6 I-1/0.7 D1/0.135 80/115 A1/10B1-22/0.2 2 A1/10 B1-21/0.6 I-1/0.7 D1/0.135 80/115 B1-22/0.2 3 A1/10 —I-1/1.5 D1/0.135 80/115 4 A1/10 — I-2/1.5 D1/0.135 80/115 5 A1/10 —I-3/1.5 D1/0.135 80/115 6 A1/10 — I-99/1.5  D1/0.135 80/115 7 A1/10 —I-103/1.5  D1/0.135 80/115 8 A1/10 — I-197/1.5  D1/0.135 80/115 Compar.A1/10  B1-2/1.5 — D1/0.135 80/115 comp 1 Compar. A2/10 B1-X1/1.5  —D1/0.135 80/115 comp 2 Compar. A2/10 B1-35/1.5 — D1/0.135 80/115 comp 3

In Table 8, each of characters represents the following component:

<Resin>

A1: Resin A1, X1: Resin X1

<Salt (I)>

I-1: Salt represented by formula (I-1)

I-2: Salt represented by formula (I-2)

I-3: Salt represented by formula (I-3)

I-99: Salt represented by formula. (I-99)

I-103: Salt represented by formula (I-103)

I-197: Salt represented by formula (I-197)

B1-21: Salt represented by formula (B1-21), prepared by the method asrecited in Example of JP2012-224611A1

B1-22: Salt represented by formula (B1-22), prepared by the method asrecited in Example of JP2012-224611A1

B1-2: Salt represented by the following formula, prepared by the methodas recited in Example of J92006-257078A1

B1-X1: Salt represented by the following formula, prepared by the methodas recited in Example of JP2012-193170A1

B1-35: Salt represented by the following formula, prepared by the methodas recited in Example of JP2009-46479A1

<Quencher >

D1: The compound of the following formula, which was manufactured byTokyo Chemical Industries, Co., Ltd.

<Solvent>

Mixture of the following solvents

propyleneglycolmonomethylether acetate 100 partspropyleneglycolmonomethylether  20 parts

<Evaluation>

On 12 inch-diameter silicon wafer having a SiO₂ layer with 100 nm inthickness, hexamethyldisilazane was applied and then the obtained onewas baked at 120° C. for 60 seconds.

One of the photoresist compositions prepared as above was spin-coatedover the baked one so that the thickness of the resulting film became240 nm after prebaked. The silicon wafer thus coated with the respectivephotoresist composition was prebaked on a direct hotplate at thetemperature as listed in the column “PB” of Table 8 for 60 seconds.

Using an ArF excimer stepper for immersion exposure (“XT: 1900Gi”manufactured by ASML, NA=1.35, Annular σout=0.85, σin=0.65, XY-pol.Illumination) and a mask for preparing line-and-space pattern (pitch:300 nm, space width: 114 nm), the wafer having the composition film wassubjected to the exposure with the exposure quantity being variedstepwise. Ultrapure water was used for immersion solvent.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at the temperature as listed in the column “PEB” of Table 8for 60 seconds and then to development for 60 seconds at 23° C. with2.38% by mass aqueous tetrametylammonium hydroxide solution in themanner of paddle development to produce positive photoresist patterns.

Effective sensitivity (ES) was defined as the exposure quantity withwhich exposure provides a pattern with 130 nm of the space width afterdevelopment, the pattern being observed with a scanning electronmicroscope.

Determining Line edge roughness:

The line-and-space patterns were produced according to theabove-mentioned procedure in which the exposure step was conducted atthe effective sensitivity.

The wall surface of the photoresist pattern was observed using ascanning electron microscope, and the irregularity in wall surface wasdetermined. Here, the roughness width means the difference of thelargest value and the smallest value as to the wall width. Table 9illustrates the results thereof.

The figures mean roughness width values (nm).

TABLE 9 Ex. No. Composition No. LER value (nm) Ex. 7 1 4.42 Ex. 8 2 4.44Ex. 9 3 4.58 Ex. 10 4 4.42 Ex. 11 5 4.55 Ex. 12 6 4.36 Ex. 13 7 4.69 Ex.14 8 4.12 Comp. Ex. 1 Compar. Comp. 1 5.19 Comp. Ex. 2 Compar. Comp. 25.08 Comp. Ex. 3 Compar. Comp. 3 5.14

The salt of the present invention is useful as a component for aphotoresist composition, and the photoresist composition containing thesalt of the present invention can provide photoresist patterns withsmaller LER.

1. A salt represented by the formula (I):

wherein Q¹ and Q² independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group, R¹ and R² independently each represent ahydrogen atom, a fluorine atom or a C1-C6 perfluoroalkyl group, zrepresents an integer of 0 to 6, L¹ represents a C1-C36 divalenthydrocarbon group which optionally has a substituent and in which amethylene group optionally is replaced by —O—, —S—, —CO— or —SO₂—, W¹represents a C3-C18 cyclic hydrocarbon group which optionally has asubstituent and in which a methylene group optionally is replaced by—O—, —S—, —CO—or —SO₂—, L² represents a single bond or a C1-C6alkanediyl group which optionally has a substituent and in which amethylene group optionally is replaced by —O— or —CO—, and R³, R⁴ and R⁵independently each represent a C1-C6 hydrocarbon group in which amethylene group optionally is replaced by —O—, and Z⁺ represents anorganic cation.
 2. The salt according to claim 1 wherein L² represents asingle bond or a C1-C6 alkanediyl group in which a methylene groupoptionally is replaced by —O— or —CO—.
 3. The salt according to claim 1wherein L¹ represents a C1-C8 alkanediyl group in which a methylenegroup optionally is replaced by —O— or —CO—, or a group composed of aC1-04 alkanediyl group in which a methylene group optionally is replacedby —O— or —CO— and a C3-C12 cyclic hydrocarbon group in which amethylene group optionally is replaced by —O—, —S—, —CO— or —SO₂—. 4.The salt according to claim 1 wherein W¹ represents an adamantane ring,a norbornane ring, a norbornene ring, a cyclohexane ring or anorbornanelactone ring.
 5. The salt according to claim 1 wherein R³, R⁴and R⁵ independently each represent a C1-C6 alkyl group.
 6. An acidgenerator comprising the salt according to claim
 1. 7. A photoresistcomposition comprising the acid generator according to claim 6 and aresin which comprises a structural unit having an acid-labile group. 8.The photoresist composition according to claim 7 which further comprisesa salt generating an acid weaker in acidity than an acid generated fromthe acid generator.
 9. A process for producing a photoresist patterncomprising the following steps (1) to (5): (1) a step of applying thephotoresist composition according to claim 7 on a substrate, (2) a stepof forming a composition film by conducting drying, (3) a step ofexposing the composition film to radiation, (4) a step of baking theexposed composition film, and (5) a step of developing the bakedcomposition film thereby forming a photoresist pattern.
 10. A processfor producing a photoresist pattern comprising the following steps (1)to (5): (1) a step of applying the photoresist composition according toclaim 8 on a substrate, (2) a step of forming a composition film byconducting drying, (3) a step of exposing the composition film toradiation, (4) a step of baking the exposed composition film, and (5) astep of developing the baked composition film thereby forming aphotoresist pattern.